Method for applying a film to a carrier by means of electrostatic charging

Description

[0001] The present invention relates to a method for producing a decorative panel, comprising applying a film to a substrate. The present invention particularly relates to a method in which a film is laminated to a substrate during the manufacturing process of a decorative panel.

[0002] For the purposes of the invention, the term "decorative panel" refers to wall, ceiling, door, or floor panels that feature a decorative pattern applied to a carrier plate. Decorative panels are used in a variety of ways, both in the interior design of rooms and for the decorative cladding of buildings, for example, in trade fair construction. One of the most common uses for decorative panels is as floor coverings or for cladding ceilings, walls, or doors. These decorative panels often feature a pattern and surface structure intended to imitate a natural material.

[0003] During the production of a decorative panel, for example, it may be desirable to laminate a film onto a substrate. The film-laminated substrate can then undergo further treatment steps or remain as is.

[0004] A disadvantage of the prior art processes is that microbubble formation may occur after a film is laminated to a substrate. However, this can reduce the quality of the product and therefore lead to rejects.

[0005] DE 2201472 A1 discloses a method for producing coated plates, wherein coating foils are applied to the top and / or bottom of the plates to be coated and then fixed to the plates to be coated. The coating foils and / or the plates to be coated are electrostatically charged, and the coating foils are fixed to the plates to be coated by the electrostatic forces.

[0006] WO 2018 / 141912 A1 discloses a method for treating PVC sheets, as well as sheets and panels produced therefrom. The invention further relates to sheets and panels, in particular wall, ceiling, or floor panels, comprising a heat-treated carrier sheet based on polyvinyl chloride with a density of, for example, 900 to 2,500 kg / m3 and a film attached thereto. The film is a thin PVC film and includes a decorative pattern printed directly onto it.

[0007] Laminating a film onto a substrate, for example in the production of a decorative panel, may therefore still offer potential for improvement.

[0008] It is therefore the object of the present invention to at least partially overcome at least one disadvantage of the prior art. Specifically, the object of the present invention is to provide a solution for improved lamination of a film onto a substrate, for example, in the context of the production of a decorative panel.

[0009] This object is achieved by a method for producing a decorative panel comprising applying a film to a carrier having the features according to claim 1. Preferred embodiments of the invention are specified in the subclaims or in the description.

[0010] The invention proposes a method for producing a decorative panel comprising applying a film to a carrier, comprising the method steps: a) providing a carrier to be provided with the film, b) providing a film, and c) applying the film to at least a partial area of ​​the carrier, g) introducing locking means at the edge of the carrier, and h) applying a decoration to the carrier before applying the film to the carrier or applying a decoration to the film, characterized in that d) the film is electrostatically charged before being applied to the carrier, and e) the carrier is electrostatically charged before being applied to the film, wherein f) the electrostatic charging of the carrier (14) and the film (12) is carried out in such a way that the film (12) and the carrier (14) are oppositely electrostatically charged, wherein the film (12) is positively charged to a range of ≥ 50V to ≤ 150V and the carrier (14) is negatively charged to a range of ≥ -750V to ≤ -150V.

[0011] Such a method can enable an improved application of a film to a carrier in the manufacturing process of a decorative panel.

[0012] This process is used primarily for applying a film to a substrate. This type of process is also known as lamination and can, in principle, be used in a wide variety of applications. However, it can be particularly advantageous if the described process is used in the production of a decorative panel.

[0013] The procedure includes the following steps.

[0014] First, according to process step a), a carrier is provided which is to be provided with the film or to which the film is to be applied. The type of carrier is not fundamentally limited, insofar as the carrier can serve as a base or substrate for the film. In other words, a carrier can basically be understood as any structure which serves as a substrate for a film to be laminated. In the case of the production of a decorative panel, however, the carrier can be a suitable carrier for this purpose. A carrier can then be understood in particular as a layer serving as the core or base layer in a finished panel, which can in particular comprise a natural material, such as a wood-based material, a fiber material or a material comprising a plastic. For example, the carrier can impart suitable stability to a panel or contribute to this.The carrier can, in particular, be a web-like carrier or a plate-like carrier. According to the invention, such a carrier is made of plastic, whereby such a carrier can be made of pure plastic or a plastic material. A plastic material should be a material that, in addition to the pure plastic, can also contain other components, in particular fillers, such as mineral or inorganic components.

[0015] Furthermore, the method according to method step b) comprises providing a film to be applied to the carrier. The design of the film is not fundamentally limited and depends in particular on the subsequent use of the film or of the composite of film and carrier. According to the invention, the film is made of a plastic, preferably a thermoplastic. For example, the film can be provided by means of a feed device, wherein the film can be guided to the carrier and onto its surface, for example using rollers.

[0016] Subsequently, according to process step c), the film is applied to at least a partial area of ​​the carrier. Thus, for example, the entire carrier, such as an entire surface of the carrier, can be coated with the film, or the carrier can be coated with the film only partially.

[0017] This can be achieved, for example, by guiding the film to the carrier as described above and then pressing it onto the carrier, for example by means of a roller, using a temperature elevated above room temperature (22°C) and a pressure elevated above ambient pressure (1 bar). This process step can also be described as lamination and can, in principle, be carried out in a selectable form. For example, the invention is intended to encompass wet lamination or dry lamination, in which the lamination is carried out using a wet or dry laminating agent. For example, a lacquer layer can be provided on the carrier, for example on a decoration applied to the carrier, which serves as a liquid laminating agent. However, a dry laminating agent is also possible in principle.

[0018] Furthermore, as indicated above, thermal lamination is included, in which the lamination is carried out at elevated temperature and pressure, but in particular without a laminating agent. The parameters to be selected, such as temperature and pressure, can be selected in a manner understandable by a person skilled in the art based on the materials of the carrier and the film.

[0019] Thermal lamination parameters depend on the material. Generally, the thermal lamination parameters for the film and carrier material should be selected in the range above the Vicat softening point for thermoplastic materials and below the melting point (for (semi-)crystalline polymers), and also above the Tg, for example, for PET. If the thermal parameters have been optimized, only very low pressure is necessary. This is particularly true if the carrier and film are well matched. Example values ​​include a temperature of 140 to 155 °C and a pressure of 1 to 10 bar for polypropylene, or a temperature of 90 to 110 °C and a pressure of 1 to 10 bar for PETG (glycol-modified PET).

[0020] If the carrier and film are made of different polymers, an adhesive and / or bonding layer or hotmelt should always be used as a lamination agent. Coextruded thermoplastic functional layers that are firmly bonded to the carrier or film during production are also conceivable as a bonding layer, such as EVA (ethylene-vinyl acetate copolymer) or a grafted MAH (maleic anhydride-grafted polymer). The lamination parameters are then adjusted to these functional layers between the film and carrier. Example parameters for EVA include a temperature of 70°C to 100°C, depending on the vinyl acetate content in the EVA, and a pressure of 1 to 10 bar.

[0021] After this step, the film can be firmly fixed to the substrate. If necessary, post-treatment, such as drying or curing of the laminating agent or film, can be performed.

[0022] In the described method, it is further provided that, according to method step d), the film is electrostatically charged before being applied to the carrier, and that, according to method step e), the carrier is electrostatically charged before the film is applied to the carrier. Electrostatic charging can in principle be carried out as is known from the prior art in other fields and described in detail later. In principle, however, it is provided that the electrostatic charging of the carrier and the film is carried out in such a way that the film and the carrier are oppositely electrostatically charged. According to the invention, the carrier is negatively charged and the film is positively charged.

[0023] This process step allows for an electrostatic attraction between the carrier and the film. This allows for a particularly close bond, especially when the carrier is coated with the film over a large area.

[0024] The film's close contact and continued adhesion to the substrate can thus reliably prevent air inclusions or at least significantly reduce them compared to prior art processes. Furthermore, by preventing or reducing air inclusions, the formation of bubbles, such as microbubbles, can also be prevented or at least significantly reduced. This allows for a particularly high surface quality, so that rejects, or rejects due to bubbles, can be reduced or even completely prevented.

[0025] Furthermore, long-term stability can be improved. Because the film adheres tightly to the carrier prior to lamination, caused by the electrostatic charges on the carrier and film, the lamination process can also enable particularly tight adhesion of the film to the carrier. This can significantly reduce the risk of the film subsequently detaching from the carrier. Even with a possibly similar charge on the film and carrier, the risk of detachment cannot be ruled out. However, this can now be prevented according to the invention.

[0026] The advantages described above, resulting from appropriate charging of the carrier and film, can be easily achieved using the process described here, even in existing film lamination systems. To implement the described process, only appropriate devices for electrostatically charging the film and carrier need to be provided, which can usually be easily retrofitted even in existing systems.

[0027] According to the invention, the electrostatic charging takes place in such a way that the film is positively charged and the carrier is negatively charged. It has been shown that the processing of film and carrier with such a charge is possible without any problems. Furthermore, according to the invention, but particularly effective in this embodiment, a reduction in the amount of lacquer applied, for example as a laminating agent in wet lamination, can be made possible, for example a reduction down to 40g / m 2< , for example down to 30g / m 2< or even less. Furthermore, according to the invention, but particularly effective in this embodiment, a reduction in the calender pressure can be made possible, which can reduce wear.

[0028] The film is charged to a voltage range of ≥ 50V to ≤ 150V, preferably ≥ 80V to ≤ 120V, approximately 100V. Additionally, the carrier is charged to a voltage range of ≥ -750V to ≤ -150V, preferably ≥ -600V to ≤ -400V, approximately -500V. Such charge values ​​can be easily implemented, even using readily available electrostatic charging agents. Furthermore, such opposite charging can particularly effectively enable intimate, even large-area, adhesion of the film to the plate, thereby permitting further processing and transport of the components without significantly negatively impacting these steps.

[0029] It may further be preferred that at least one of the carrier and the film be electrostatically discharged prior to electrostatic charging. In this embodiment, the aforementioned advantages can be achieved particularly reliably and precisely. Electrostatic charging after electrostatic discharging can achieve a particularly defined and homogeneous electrostatic charging in a precisely defined area, as local charge peaks can be prevented.

[0030] For example, a discharge can be carried out in a range from greater than 0 kV to less than or equal to 20 kV. Particularly preferably, the film and the carrier are discharged to a charge value of 0 before electrostatic charging.

[0031] With regard to electrostatic charging and electrostatic discharging, it may further be preferred that a device for applying electrostatic charges for carrying out method step d) or e) comprises at least one of a strip, roller, brush, or lip formed at least partially from an electrically conductive material and an ion beam device. Alternatively or additionally, it may be provided that a device for discharging electrostatic charges comprises at least one of a strip, roller, brush, or lip formed at least partially from an electrically conductive material and an ion beam device.

[0032] For example, a device for supplying or discharging electrostatic charges or for discharging electrostatic charges can be designed as a strip which makes electrically conductive contact with the carrier and / or the film and which preferably has an arrangement which runs essentially parallel to a surface of the film and / or the carrier and is oriented transversely to the direction of travel of the film or the carrier. Essentially parallel can in particular mean a deviation or tolerance of ≤ 20%, in particular ≤ 10%, for example ≤ 1% of the distance between the surface of the strip and the surface of the film or the carrier. In principle, the strip can be positioned above and / or below the surface to be loaded. With such a configuration, even large areas can be loaded and unloaded in a homogeneous and defined manner.

[0033] Alternatively or additionally, it may be provided that the device for discharging electrostatic charges and / or applying electrostatic charges comprises at least one roller, brush or lip made of a conductive material, which makes electrically conductive contact with the carrier and / or the film.

[0034] During a discharge, the corresponding device for discharging electrical charges may be connected to an electrical ground potential. The electrical ground potential may be provided, for example, by grounding. During a charging, the device for supplying electrical charges may be connected to a charge source.

[0035] The strip, roller, brush or lip is preferably formed, at least in the contact area with the lacquer-containing top layer, from a material with a conductivity ≥ 1*10 3< Sm -1<.

[0036] Furthermore, the loading and / or unloading device may include an ionization device, by means of which an ionized air jet is directed over the surface of the film or carrier. Such a device may also be referred to as an ion beam device. It has been shown that exposure to ionized air is suitable for further reducing or increasing the occurrence of electrostatic charging of the carrier.

[0037] According to the invention, the carrier is made of a plastic. Particularly preferably, the carrier can comprise a material comprising a plastic and optionally further components. Plastics that can be used in the production of corresponding panels or the carriers are, for example, thermoplastics, such as polyvinyl chloride, polyolefins (e.g. polyethylene (PE), polypropylene (PP), polyamides (PA), polyurethanes (PU), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyetheretherketone (PEEK) or mixtures or copolymers thereof. The plastics can contain conventional fillers, for example calcium carbonate (chalk), aluminum oxide, silica gel, quartz powder, wood flour, gypsum. They can also be colored in a known manner.The carrier can preferably contain talc as a filler material, for example in an amount, based on the total material of the carrier, of ≥ 30 wt.% to ≤ 70 wt.%, in particular of ≥ 40 wt.% to ≤ 60 wt. Furthermore, the carrier can be multilaminar, i.e., composed of a plurality of films. The films can be the same as or different from the film to be laminated.

[0038] Such plastic supports are particularly preferred for decorative panels for many applications and can also be easily electrostatically charged and discharged, so that the method can be carried out without problems, especially in this embodiment.

[0039] According to the invention, the film is made of plastic, for example consists thereof or also has further components. More precisely, the film can comprise an acrylate-based plastic composition, in particular a polyurethane-modified acrylate plastic composition, wherein the film comprises the plastic composition in an at least partially, for example completely, cured form, so that it can be transported and treated accordingly for lamination. Any necessary final curing of the film can optionally take place in a further step following lamination. This can be done, for example, using high-energy and short-wave UV radiation and leads to the radical polymerization of the acrylate groups and additional cross-linking of the monomers. This considerably increases the surface hardness.

[0040] This advantageously ensures that the film is flexible overall and at the same time has particularly good protective properties such as stability, scratch resistance, heat resistance, water resistance and the like for a wide range of applications, for example as a protective layer of a decorative panel.

[0041] The plastic composition of the film can preferably comprise a dipropylene glycol diacrylate, preferably in an amount of > 0 to ≤ 15 wt.% based on the plastic composition, and a reaction product of pentaerythritol, epichlorohydrin and acrylic acid, preferably in an amount of ≥ 2 to ≤ 15 wt.% based on the plastic composition.

[0042] Furthermore, the film can also be made of other, particularly thermoplastic, plastics, such as polyethylene terephthalate (PET).

[0043] Furthermore, it may be preferred for the film to be applied to the carrier by thermal lamination. This embodiment can be particularly advantageous since an additional laminating agent can be dispensed with. This makes the process simple to implement with regard to the peripherals and can also be cost-effective. Treatment at elevated temperature and pressure can be easily implemented, particularly with plastic films, for example as described above. The electrostatic charging of film and carrier described above can also enable a strong and long-term stable bond between carrier and film despite the lack of a laminating agent.

[0044] The method according to the invention for producing a decorative panel comprises the following further process steps: g) applying locking means to edges of the substrate; and h) applying a decoration to the substrate before applying the film or applying a decoration to the film.

[0045] In this process, a described lamination of the film is used to form a decorative panel. The carrier is a plastic carrier and the film is a plastic film as described above.

[0046] To form a decorative panel, locking elements are provided along the edges of the support, for example, all the way around. This can be achieved, for example, by machining the support edges, as is generally known from the prior art. This allows a stable composite to be created from a large number of panels in a similarly known manner, as a floor covering, ceiling covering, or wall covering.

[0047] With regard to the construction of the panel, the film can be provided at various positions in the panel structure. For example, the film can serve as a decorative base, so that the film can be laminated directly onto the carrier material or another layer of the carrier and the film can then be provided with a decoration, in particular imitating a decorative template, for example using a digital printing process. Furthermore, the film can be printed before being applied to the carrier and thus serve as a decorative film. The film can thus be provided with a decoration, in particular printed, before or after being applied to the carrier.

[0048] Accordingly, it can be provided that process step h) comprises printing the carrier before applying the film to the carrier and / or process step h) comprises printing the film before or after applying the film to the carrier.

[0049] It may be preferred if the film is used as a wear film. In this embodiment, process step h) can thus comprise printing the carrier before applying the film. The printing of the carrier can again be carried out using a digital printing process.

[0050] When the film is designed as a protective layer or wear layer, the film can serve as a protective layer and cover the decoration upwards in order to protect the decoration and the carrier from external influences.

[0051] The film can be designed to serve as a wear-resistant base film and be provided with a tactile feel. To protect the applied decorative layer, wear or covering layers are usually applied above the decorative layer. Often, a surface structure imitating a decorative template is incorporated into such wear or covering layers, so that the surface of the decorative panel has a tactile structure whose shape and pattern are adapted to the applied decoration, thus achieving the most faithful reproduction of a natural material, including in terms of feel.

[0052] To apply the haptic effect, it may be provided that a further layer is applied to the film, which is provided with a structure. For this purpose, it may be preferred that after the film has been applied to the carrier, the film is provided with a structured lacquer layer or with a lacquer-containing cover layer, i.e. with a lacquer layer that is structured and cured. The latter can be done, for example, using UV radiation. In particular, if the film and the lacquer are made of the same material, for example as described above, a final curing of the film can also take place during curing, for example final curing, of the lacquer to fix the structure. Structuring of the lacquer can be done, for example, using a press or printing with a displacement ink, whereby the lacquer layer is preferably partially cured before the structure is introduced.

[0053] Furthermore, a further film can be laminated on, in particular according to the method described above, which is then provided with a structure.

[0054] Alternatively, the film itself can be provided with a structure. This can be achieved, for example, by providing the laminated film with a structure after it has been applied to the carrier or by providing the film to be laminated with a structure before it is applied to the carrier, for example by means of embossing.

[0055] It can further be provided that the film and / or the lacquer-containing top layer comprises hard materials, preferably in an amount between ≥ 5 wt.% and ≤ 40 wt.%, wherein the hard materials preferably have an average grain diameter between 10 µm and 250 µm. Examples include titanium nitride, titanium carbide, silicon nitride, silicon carbide, boron carbide, tungsten carbide, tantalum carbide, aluminum oxide (corundum), zirconium oxide, zirconium nitride, or mixtures thereof.

[0056] With regard to further advantages and technical features of the method for producing a decorative panel, reference is made to the description of the method for applying a film to a carrier, the figure and the further description.

[0057] The invention is further explained below with reference to a figure.

[0058] It shows: Fig. 1 a schematic representation of an arrangement for carrying out a method according to the invention.

[0059] In the Figure 1 An arrangement 10 is shown by means of which a film 12 can be applied to a carrier 14. For this purpose, a feed device 16 is shown, by means of which the film 12 can be provided. The feed device 16 comprises, for example, a deflection roller 18. Furthermore, a transport system 20 is shown, on which a plurality of plate-shaped carriers 14 can be conveyed. The transport system 20 comprises circulating belts 24 guided by rollers 22, on which the carriers 14 rest.

[0060] Also shown are calender rolls 26, 28, between which a roll nip 30 can be formed. The carrier 14 runs on the belts 24 into the roll nip 30, and the film 12 is guided by the calender roll 26 into the roll nip 30 onto the carrier 14. In the view according to the figure, the carrier 14 and film 12 run from the right side to the left into the mill gap 30. The film 12 can be applied to the carrier 14 in the roll nip 30. For this purpose, the calender rolls 26, 28, or at least the calender roll 26 guiding the film 12, can be heated if necessary, and the calender rolls 26, 28 can exert contact pressure between the film 12 and the carrier 14. The film 12 can thus be applied to the carrier 14, for example, by means of thermal lamination. However, it should be mentioned that in principle the carrier 14 can also be heated and that freely selectable heating means can be used for heating the carrier 14 and the film 12.

[0061] Behind the calender rolls 26, 28 or after the roll gap 30, the film 12 is firmly connected to the carrier 14 during thermal lamination.

[0062] When using a laminating agent, such as a varnish, this can be cured by the radiation unit 36, which emits UV radiation, for example. This allows the film 12, which is merely in the adhesive bed before the radiation unit 36, to adhere firmly to the carrier 12 after the radiation unit 36. For example, the radiation unit 36 ​​can be arranged approximately 200 mm after the roller nip 30.

[0063] Subsequently, further processing steps can follow, such as applying a structured lacquer layer to the film 12 or, more generally, structuring the surface. Furthermore, locking means can be introduced into the edges of the carrier 14 before or after the roller gap 30, for example, if the method is to be used in the production of a decorative panel. In the latter case, for example, a decoration can also be applied to the carrier 14, which can also be done before or after the roller gap 30.

[0064] To enable particularly high-quality application of the film to the carrier, a device 32 for applying electrostatic charges to the film 12 is also provided, as is a device 34 for applying electrostatic charges to the carrier 14. The devices 32, 34 are each designed as a strip, which preferably has an arrangement extending substantially parallel to a surface of the film 12 or the carrier 14 and oriented transversely to the direction of travel of the film 12 or the carrier 14.

[0065] This makes it possible for the film 12 to be electrostatically charged before being applied to the carrier 14, and for the carrier 14 to be electrostatically charged before the film 12 is applied to the carrier 14. More specifically, the electrostatic charging of the carrier 14 and the film 12 should be carried out in such a way that the film 12 and the carrier 14 are electrostatically charged in opposite directions.

[0066] In detail, it is provided that the film 12 is positively charged and that the carrier 14 is negatively charged, wherein the film 12 is charged to a range of ≥ 50V to ≤ 150V and wherein the carrier 14 is charged to a range of ≥ -750V to ≤ -150V.

[0067] Not shown are optional devices that enable at least one of the carrier 14 and the film 12, for example both the carrier 14 and the film 12, to be electrostatically discharged before electrostatic charging. List of reference symbols

[0068] 10Arrangement 12Film 14Carrier 16Feeding device 18Deflection roller 20Transport system 22Roller 24Belt 26Calender roller 28Calender roller 30Roll gap 32Device for applying electrostatic charges 34Device for applying electrostatic charges 36Radiation unit

Claims

1. Method for producing a decorative panel comprising the application of a film (12) to a substrate (14), including the method steps: a) providing a substrate (14) to be provided with the film (12), wherein the substrate (14) is made of plastic; b) providing a film (12); and c) applying the film (12) onto at least a partial area of the substrate (14), wherein the film (12) is made of plastic, wherein d) the film (12) is electrostatically charged before being applied to the substrate (14), wherein e) the substrate (14) is electrostatically charged before the film (12) is applied to the substrate (14), g) inserting interlocking means at edges of the substrate (14); and h) applying a decoration onto the substrate (14) prior to applying the film (12) to the substrate (14) or applying a decoration onto the film (12), characterized in that in a step f) the electrostatic charging of the substrate (14) and the film (12) are carried out in such a way that the film (12) and the substrate (14) are electrostatically charged oppositely, wherein the film (12) is positively charged to a range of ≥ 50 V to ≤ 150 V and the substrate (14) is negatively charged to a range of ≥ -750 V to ≤ -150 V.

2. Method according to any one of the preceding claims, characterized in that a device (32, 34) for applying electrostatic charges for carrying out method step d) or e) comprises at least one of a strip, a roller, a brush, a lip formed at least partially from an electrically conductive material, and an ion beam device.

3. Method according to any one of the preceding claims, characterized in that at least one of the substrate (14) and the film (12) is electrostatically discharged prior to electrostatic charging.

4. Method according to claim 6, characterized in that a device for dissipating electrostatic charges comprises at least one of a strip, a roller, a brush, a lip formed at least partially from an electrically conductive material, and an ion beam device.

5. Method according to claim 1, characterized in that the application of the film (12) to the substrate (14) is carried out as thermo lamination or as wet lamination.

6. Method according to any one of the preceding claims, characterized in that method step h) comprises printing the substrate (14) before applying the film (12) to the substrate (14).

7. Method according to any one of the claims 1 to 5, characterized in that method step h) comprises printing the film (12) before or after applying the film (12) to the substrate (14).

8. Method according to any one of the preceding claims, characterized in that the film (12) is provided with a structure.

9. Method according to any one of the preceding claims, characterized in that a further layer is applied to the film (12), which is provided with a structure.