Device, set, and method for welding at least two film sections to one another

Abstract

The invention relates to: a device (10) for welding at least two film sections (12) to one another, having the features of claim 1; a set (30) for welding at least two film sections (12) to one another, the set comprising at least one such device (10) and at least two film sections (12), having the features of the claim; and a method for welding at least two film sections (12) to one another, having the features of claim 12.

Description

[0001] Title : Device, set and method for welding at least two film sections together

[0002] Description

[0003] The invention relates to a device for welding at least two film sections together with features of claim 1, a set for welding at least two film sections together comprising at least one such device and at least two film sections with features of claim 10 and a method for welding at least two film sections with features of claim 12.

[0004] Conventional thermal sealing or welding of monomaterials such as PE (polyethylene) or PP (polypropylene) often presents difficulties. This is due in particular to some specific challenges that differ from other materials.

[0005] PE and PP have lower melting points than other plastics. This means they are more sensitive to high temperatures and can melt more quickly (e.g., at a welding jaw), which makes process control more difficult. Since heat is typically applied via heated welding jaws during welding, the contact surface between the welding jaws and the film (i.e., the outer surface of the film) becomes hotter than the surface between the films that are actually being welded. This can lead to damaged weld seams.

[0006] Monomaterials often have lower adhesion properties compared to multilayer films or other plastics. This can result in welds that are less strong and more prone to cracking.

[0007] PE and PP are particularly sensitive to moisture, which can lead to problems during welding. Moisture can change the surface properties of the films and impair adhesion.

[0008] Monomaterials can vary in quality and composition, even if they are declared as the same type. These variations can affect the welding result and require very precise process control.

[0009] The welding of monomaterials usually requires specially adapted or optimized parameters, such as:

[0010] Temperature, pressure, and welding time. These parameters have a smaller tolerance for monomaterials than for multilayer films.

[0011] Monomaterials are more easily damaged, especially if handled improperly or if inadequately protected against mechanical stress. This can lead to leaky welds.

[0012] High-frequency welding can be used to weld polar plastic films, i.e., films with a dipole moment. This process exploits the dielectric loss factor of the plastic films to be welded. High-frequency welding takes advantage of the dielectric loss factor, which is particularly effective for polar plastic films with a pronounced dipole moment. This allows the plastics to absorb a large amount of energy from the alternating electric field and heat up in the process. Suitable plastics, such as PMMA or PA12, have a high dielectric loss factor.

[0013] In contrast, PE and PP, as non-polar plastics with a very low dielectric loss factor, are extremely unsuitable for high-frequency welding, since they can absorb almost no energy from the alternating electric field compared to, for example, PMMA or PA12.

[0014] Another alternative for welding plastics is ultrasonic welding. This process uses two sonotrodes to generate ultrasonic waves that inject heat into the plastics. The disadvantage is that the outer surfaces of the plastics, i.e., the contact surfaces with the sonotrodes, are heated more than the weld between the plastic films.

[0015] The object of the present invention is to provide a device, a set and a method for welding at least two film sections together, wherein the above disadvantages are eliminated.

[0016] The above object is achieved by a device for welding at least two film sections together with the features of claim 1.

[0017] The device comprises at least two electrodes and an energy source for supplying the electrodes with electrical current and / or electrical voltage. The energy source and / or the electrodes are particularly configured to generate at least one high-frequency, high-voltage electric field between the electrodes. The energy source is particularly configured to generate a high-frequency high voltage.

[0018] The device additionally comprises a positioning device for positioning the electrodes and / or the film sections in such a way that the film sections are arranged between the electrodes and the film sections are arranged at a distance from one another. The positioning device can be set up to position the electrodes and / or the film sections in such a way that the film sections contact the electrodes, in particular with the sides of the film sections facing away from one another. The film sections and / or the electrodes can be positioned by means of the positioning device in particular in such a way that an air gap is created between the films, but no air gap is created between each film and the electrode contacting this film. For this purpose, the positioning device can comprise at least one deflection roller for tensioning or applying the film sections to the electrodes.Alternatively or additionally, the positioning device may comprise a device for extracting air (or applying a negative pressure) to the electrodes and / or the film sections in order to suck the film sections onto the respective electrode by means of negative pressure.

[0019] The film sections can be part of the same film or each form part of a separate film. If a single film is used, two areas (e.g., different edge areas) of the film can be welded together. If, for example, two separate films are used, these can be welded together.

[0020] In this way, a dielectric barrier discharge in an air gap between the two spaced-apart film sections can be used for welding. In this case, welding means sealing by means of heat input. Both polar and non-polar films can be welded together. Targeted heat input directly in the (subsequent) weld seam or at the contact point between the two film sections is possible. Heating of outer surfaces or opposite sides of the film sections is avoided. This makes it possible to optimize the heat input and thus the entire welding process. The disadvantages described above can be avoided. According to a development of the device, the device can be set up to generate a plasma between the electrodes and / or the film sections.

[0021] By means of a dielectric barrier discharge in the (narrow) air gap between the foil sections, an intensive atmospheric plasma can be generated in the air, which ultimately heats the desired welding contact point specifically where the foil sections are to be welded (namely at their common contact point).

[0022] The energy source may comprise a control device for controlling or regulating the generated electric field and the resulting plasma. The energy source may be configured as a high-frequency, high-voltage generator.

[0023] As a result of the plasma discharge, thin, in the limiting case single-molecular-layer, polar chemical groups, such as "-COH" or "-COOH, can form on the surface of (initially non-polar) foil sections due to, among other things, radicals and other high-energy short-lived species. These groups can also absorb energy from an electric field. In addition, these groups can create better adhesion between the foil sections through additional chemical polar bonds and hydrogen bridges. In this way, a hot-melt effect can be achieved directly at the weld point between the foil sections.

[0024] This allows for simple high-frequency plasma welding of polar and non-polar plastic monofilms using dielectric barrier discharge. In other words, a film sealing technology with dielectric plasma generation as the heat source can be provided.

[0025] By using monomaterial films, such as PE or PP, the packaging industry can implement more environmentally friendly packaging solutions and promote sustainability. PE and PP are easily recycled. Using monomaterial films made from these plastics can simplify recycling, as separation of different materials is not required. This can facilitate reuse and contribute to reducing plastic waste.

[0026] Multi-layer composite materials can thus be avoided. For multi-layer packaging with different

[0027] Recycling plastic layers or metal barriers is often difficult and expensive. Using monomaterials can avoid this problem, as they consist of a single type of plastic and are therefore easier to recycle.

[0028] The production of composite materials generally requires more energy and resources than the use of monomaterials. By using materials such as PE or PP, the ecological footprint of a packaging can be reduced. This can also help to mitigate the often negative environmental impacts.

[0029] When disposing of PE and PP, for example, the environmental impact tends to be lower than with some other plastics. They emit fewer harmful gases when burned and produce fewer toxic residues. According to a further development of the device, the electrodes can be designed to be movable toward and / or away from each other.

[0030] This allows the film sections to be pressed together using simple means.

[0031] The device may comprise a device for pressing the film sections together. The pressing device may have pressing tools, such as pressure rollers, which press the film sections together, for example, in the case of a longitudinal seam welding.

[0032] According to a further development of the device, at least one electrode (in particular all electrodes) can have at least one air channel and / or be porous. The air channel and / or the channels formed by the porosity can be formed as part of the positioning device. The film sections can be sucked onto the (respective) electrode through the exhaust air channel and / or through the channels formed by the porosity.

[0033] This allows the positioning device to be implemented using simple means. Alternatively or additionally, the air channel and / or the porosity can be used to cool the respective electrode.

[0034] According to a further development of the device, at least one electrode (in particular, all electrodes) can have an electrical insulation layer, at least in some regions. Alternatively or additionally, at least one electrode (in particular, all electrodes) can be arranged or embedded at least partially within an electrical insulation material. The insulation layer and / or the insulation material can, in particular, be non-polar.

[0035] This allows for simple electrical insulation of the electrodes. In particular, electrical contact between the electrodes and the foil sections can be avoided.

[0036] According to a further development of the device, the insulation layer and / or the insulation material can each be designed to be temperature-resistant. The insulation layer and / or the insulation material can each comprise ceramic or be made of ceramic.

[0037] This allows the service life of the device to be increased using simple means.

[0038] According to a further development of the device, at least one electrode (in particular, all electrodes) can have at least one (in particular, several) section tapering in the direction of the film sections. The tapered section can, in particular, be wedge-shaped or tapered. In other words, the tapered section can have a tip pointing in the direction of the film sections. At least one electrode (in particular, all electrodes) can have knurling and / or ribbing.

[0039] According to a further development of the device, the

[0040] The cooling device may comprise at least one cooling channel. The cooling channel may be arranged at least partially within at least one electrode, within the insulation layer of at least one electrode, and / or within the insulation material.

[0041] This allows for simple cooling of the electrodes, allowing the heat to be applied directly to the surfaces of the foil sections to be welded (or the weld seam). This allows the welding process to be further optimized.

[0042] The above object is further achieved by a set for welding at least two film sections together with the features of claim 10. The set comprises at least one device according to the above embodiments and at least two film sections. The film sections are made of plastic. The film sections can be film sections according to the above embodiments.

[0043] Regarding the advantages that can be achieved, reference is made to the relevant information on the device. The measures described in connection with the device and / or those explained below can be used to further refine the set.

[0044] According to a further development of the set, at least one foil section (in particular all foil sections) can be made of

[0045] Monomaterial. At least one film section (in particular all film sections) can be made of polypropylene or polyethylene. Regarding the advantages thus achieved, reference is made to the relevant information on the film sections. The measures described in connection with the film sections and / or those explained below can be used to further configure the set.

[0046] The above object is further achieved by a method for welding at least two film sections together with the features of claim 12. The method comprises the steps:

[0047] Positioning the foil sections between at least two electrodes and spaced apart from each other.

[0048] Generating a plasma between the electrodes and, at least in some areas, between the foil sections. The plasma can be a high-frequency plasma.

[0049] Pressing the foil sections together. This can be achieved using the electrodes. It is also conceivable that the foil sections can be pressed together using a separate device. The foil sections can be pressed together, in particular (immediately) after the plasma has been generated.

[0050] This allows for simple (high-frequency) plasma welding of polar and non-polar plastic monofilms using dielectric barrier discharge. In other words, a film sealing technology with dielectric plasma generation as the heat source can be provided. The above-described

[0051] Disadvantages can be avoided.

[0052] According to a further development of the method, the method may comprise the step:

[0053] Generating local increases in an electric field between the electrodes .

[0054] This allows more uniform plasma streamers to be produced and thus the welding result to be improved.

[0055] According to a further development of the method, the method may comprise the step:

[0056] Cooling at least one electrode (especially all electrodes).

[0057] This allows the heat input to be targeted into the weld seam or into the contact surfaces between the film sections, thus further optimising the welding process.

[0058] According to a further development of the method, a device according to the above statements or a set according to the above statements can be used to carry out the method.

[0059] With regard to the advantages thus achieved, reference is made to the relevant explanations of the device or set. The measures described in connection with the device or set and / or those explained below may serve to further refine the method.

[0060] Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of embodiments with reference to the drawings. They show schematically:

[0061] Fig. 1 shows a device for welding at least two film sections according to a first embodiment;

[0062] Fig. 2 shows an electrode of the device according to Figure 1 according to a second embodiment and

[0063] Fig. 3 shows an electrode of the device according to Figure 1 according to a third embodiment.

[0064] In the following description and in the figures, corresponding components and elements bear the same reference symbols. For the sake of clarity, not all reference symbols are shown in all figures.

[0065] Figure 1 schematically shows a device 10 for welding at least two film sections 12 according to a first embodiment. The device 10 comprises two electrodes 14 and a power source 16 for supplying the electrodes 14 with electrical current and / or electrical voltage.

[0066] The device 10 comprises a positioning device 18 for

[0067] Positioning the electrodes 14 and / or the film sections 12 such that the film sections 12 are arranged between the electrodes 14 and are arranged at a distance from one another. In the present case, the positioning device 18 is set up such that the film sections 12 contact the electrodes 14. An air gap 13 is arranged between the two film sections 12. In the present case, no air gap is arranged between each film section 12 and the respective electrode 14 contacting this film section 12.

[0068] In the present case, the positioning device 18 comprises four suction devices 19. The suction devices 19 are arranged and configured such that two of the suction devices 19 can each suck up a film section 12 and press it against the respective electrode 14, for example by applying a negative pressure. Thus, one film section 12 can each contact an electrode 14 (without an air gap).

[0069] In other words, the film section 12 on the left in Figure 1 is sucked in by means of the two suction devices 19 on the left in Figure 1 and pushed to the left in Figure 1 and thus pressed freely against the air gap of the electrode 14 on the left in Figure 1. Correspondingly, the film section 12 on the right in Figure 1 is sucked in by means of the two suction devices 19 on the right in Figure 1 and pushed to the right in Figure 1 and thus pressed freely against the air gap of the electrode 14 on the right in Figure 1. In the present case, one electrode 14 is arranged between each of the two suction devices 19.

[0070] It is also conceivable that the positioning device 18 for

[0071] Pressing the film sections 12 onto the electrodes 14 can additionally or alternatively comprise a plurality of deflecting bodies or rollers or other devices. It is also conceivable that the suction devices 19 can be implemented or integrated at least partially (e.g. in the form of channels) into the electrodes 14. For example, it is conceivable that the film sections 12 can be sucked through channels in the electrodes 14 (not shown) or through porous electrodes 14.

[0072] The device 10 is configured here to generate a plasma between the electrodes 14 and / or between the film sections 12.

[0073] In this case, the electrodes 14 are designed to be movable toward and away from each other. This simplifies the contacting of the film sections 12 by means of the electrodes 14. Furthermore, the film sections 12 can be pressed together by means of the movable electrodes 14, thus carrying out or finalizing the welding process.

[0074] Figure 2 schematically shows an electrode 14 of the device 10 according to Figure 1 according to a second exemplary embodiment. The device 10 according to the second exemplary embodiment differs from the device 10 shown in Figure 1 according to the first exemplary embodiment by having differently designed electrodes 14.

[0075] For the sake of clarity, the positioning device 18 is not shown here. For the same reason, only one of the two electrodes 14 and only one film section 12 are shown. The electrode 14 shown here is at least partially arranged or embedded within an electrical insulation material 20. It is also conceivable that the electrode 14 can additionally or alternatively have an electrical insulation layer at least in some regions. In the present case, the film section 12 contacts the insulation material 20. In particular, there is no air gap between the film section 12 and the insulation material 20.

[0076] The insulating material 20 and / or the insulating layer can each be designed to be temperature-resistant. In particular, the insulating layer and / or the insulating material 20 can each comprise ceramic or be formed from ceramic.

[0077] The illustrated electrode 14 has several (eleven) sections 22 that taper toward the foil sections 12 (to the right in Figure 2). The sections 22 are wedge-shaped or tapered. The sections 22 form a knurling 24. This allows for local increases in the electric field between the electrodes 14 and thus for a more homogeneous plasma streamer.

[0078] Figure 3 schematically shows an electrode 14 of the device 10 according to Figure 1 according to a third embodiment. The device 10 according to the third embodiment differs from the device 10 shown in Figure 2 according to the second embodiment in the following:

[0079] In this case, the device 10 has a cooling device 26 for cooling at least one electrode 14. The cooling device 26 comprises a plurality of (six) cooling channels 28. The cooling channels 28 are arranged at least partially within the insulation material 20. It is also conceivable that the cooling channels 28 can be arranged at least partially in the electrode 14 and / or within the insulation layer.

[0080] The device 10 and at least two film sections 12 according to the above embodiments can form a set 30. In particular, a device 10 and at least two film sections 12, each shown in Figures 1 to 3, can form a set 30. The film sections 12 are made of plastic. At least one film section 12 can be made of a single material, in particular polypropylene or polyethylene.

[0081] In the following, a method for welding at least two film sections 12 together is described with reference to Figures 1 to 3:

[0082] The procedure includes the following steps:

[0083] Positioning the film sections 12 between at least two electrodes 14 and spaced apart from each other (see Figure 1).

[0084] Generating a plasma between the electrodes 14 and at least partially between the film sections 12.

[0085] Pressing the foil sections 12 together. This can be done using the electrodes 14. The electrodes 14 can be designed to be movable for this purpose. The pressing of the foil sections 12 together can be carried out (immediately) after the plasma has been generated.

[0086] The process may comprise one or more of the following steps:

[0087] Generating local increases in an electric field between the electrodes 14. This allows plasma streamers to be made uniform.

[0088] Cooling at least one electrode 14 .

[0089] Carrying out the method by means of a device 10 according to the above statements or a set 30 according to the above statements. The method can in particular be carried out by means of a

[0090] Device 10 or a set 30, each of which is shown in Figures 1 to 3.

Claims

Patent claims 1. Device (10) for welding at least two film sections (12) together, comprising: at least two electrodes (14), an energy source (16) for supplying the electrodes (14) with electrical current and / or electrical voltage, a positioning device (18) for positioning the electrodes (14) and / or the film sections (12) such that the film sections (12) are arranged between the electrodes (14), in particular contact the electrodes (14), and that the film sections (12) are arranged at a distance from one another.

2. Device (10) according to claim 1, characterized in that the device (10) is designed to generate a plasma between the electrodes (14) and / or the film sections (12).

3. Device (10) according to claim 1 or 2, characterized in that the electrodes (14) are designed to be movable towards and / or away from each other.

4. Device (10) according to one of the preceding claims, characterized in that at least one electrode (14) has at least one air channel and / or is porous.

5. Device (10) according to one of the preceding claims, characterized in that at least one electrode (14) has an electrical Insulation layer and / or is at least partially arranged within an electrical insulation material (20).

6. Device (10) according to the preceding claim, characterized in that the insulation layer and / or the insulation material (20) are each designed to be temperature-resistant, in particular comprise ceramic or are made of ceramic.

7. Device (10) according to one of the preceding claims, characterized in that at least one electrode (14) has at least one, in particular several, in the direction of the film sections (12) tapered, in particular wedge-shaped, section (22), in particular a knurling (24) and / or a corrugation.

8. Device (10) according to one of the preceding claims, characterized in that the device (10) comprises at least one cooling device (26) for cooling at least one electrode (14).

9. Device (10) according to the preceding claim, characterized in that the cooling device (26) comprises at least one cooling channel (28), wherein the cooling channel (28) is arranged at least in regions within at least one electrode (14), within the insulation layer of at least one electrode (14) and / or within the insulation material (20).

10. Set (30) for welding at least two film sections (12) together, comprising at least one device (10) according to one of the preceding Claims and at least two film sections (12), wherein the film sections (12) are made of plastic.

11. Set (30) according to claim 10, characterized in that at least one film section (12) is made of monomaterial, in particular of polypropylene or polyethylene.

12. A method for welding at least two film sections (12) together, comprising the steps of: Positioning the film sections (12) between at least two electrodes (14) and spaced apart from one another; - generating a plasma between the electrodes (14) and at least partially between the film sections (12); Pressing the film sections (12) together, in particular by means of the electrodes (14).

13. The method according to claim 12, characterized in that the method comprises the step: Generating local increases in an electric field between the electrodes (14) .

14. The method according to claim 12 or 13, characterized in that the method comprises the step: Cooling at least one electrode (14).

15. Method according to one of claims 11 to 14, characterized in that for carrying out the method a device (10) according to one of claims 1 to 9 or a set (30) according to claim 10 or 11 is used.

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