Method for producing injection-molded part, injection-molded part and intermediate product

Abstract

The invention relates to a method for producing an injection molded part (50), in which the following steps are carried out, in particular in the following order: a) providing an insert film or insert sheet, in which the insert film or insert sheet (10) comprises a haptic layer (11); b) applying a buffer protective film comprising an adhesive layer (21) and a buffer layer (22) onto the haptic layer (11) of the insert film or insert sheet (10); c) embedding the insert film or insert sheet (10) in an injection mold (60) of an injection molding machine such that the buffer protective foil (20) is in contact with a wall of the injection mold (60), d) back injection molding the insert film or insert sheet (10) with a plastic compound to provide an injection-molded part (50), e) removing the injection-molded part (50) from the injection mold (60).

Description

Technical Field

[0001] The invention relates to a method for producing an injection-molded part as well as to an injection-molded part and an intermediate product. Background Art

[0002] To produce decorative molded parts, an insert molding process is typically used. To this end, an insert, which can be an insert film or an insert sheet, is back-injected with a plastic compound in an injection molding machine. In order to provide an injection molded part with a tactilely perceptible surface, these insert sheets or insert films include a tactile layer. The tactile layer then forms the outermost layer of the injection molded part. Typically, these insert sheets or insert films are first deep-drawn or vacuum-formed before back-injection molding. The preformed insert sheet or insert film is then placed in an injection molding machine and back-injected. Due to the high temperatures and high pressures during injection molding, deep-drawing, and vacuum forming, the outer tactile layer is severely damaged and deformed. This results in a reduced tactile effect that does not meet customer requirements in terms of touch or visual appearance. Summary of the Invention

[0003] It may be an object to provide a method for producing an injection-molded part comprising a haptic structure and an injection-molded part comprising a haptic structure, wherein the generated haptic effect is improved.

[0004] This object is achieved by a method for producing an injection-molded part, wherein the following steps are carried out, in particular, in the following order:

[0005] a) providing an insert film or insert sheet, wherein the insert film or insert sheet comprises a tactile layer;

[0006] b) applying a buffer protective film comprising an adhesive layer and a buffer layer to the tactile layer of the insert film or insert sheet;

[0007] c) inserting the insert film or insert sheet into an injection mold of an injection molding machine so that the buffer protection foil is in contact with a wall of the injection mold;

[0008] d) back injection molding the insert film or insert sheet with a plastic compound to provide an injection molded part;

[0009] e) Removing the injection molded part from the injection mold.

[0010] The object is also achieved by an injection-molded part produced, in particular, by a method according to one of claims 1 to 29,

[0011] Therein, the injection-molded component comprises a base body composed of a plastic compound and a tactile layer fixedly connected to the base body.

[0012] Furthermore, the object is achieved by an intermediate product comprising an injection-molded part according to one of claims 30 to 36, preferably produced by a method according to one of claims 1 to 29, wherein the intermediate product further comprises a releasable buffering protective foil, the buffering protective foil being adjacent to the tactile layer, wherein the buffering protective foil comprises an adhesive layer and a buffering layer.

[0013] The present invention now makes it possible to provide an injection-molded part with an external tactile layer, whereby the tactile layer remains essentially unchanged in shape compared to the tactile layer of the embedded sheet or film in the undeformed state. In other words, the tactile structure or tactile layer of the finished injection-molded part is not deformed at all or only minimally. This is achieved in particular by the fact that the cushioning protective foil is the layer that comes into contact with the mold wall during the forming process, such as deep drawing, vacuum forming, or injection molding, and acts as a damping layer. The high pressures and temperatures prevailing during the forming process compress the cushioning protective foil but not the tactile layer. The result is an injection-molded part with an external tactile layer whose structure has a high-quality optical appearance and is also very easy to perceive through tactile perception.

[0014] Layer and / or film are understood to mean in particular a substantially planar structure, which is respectively single-layered or multi-layered. The film is preferably self-supporting. The layer is, for example, self-supporting or non-self-supporting.

[0015] Advantageous embodiments of the invention are described in the dependent claims.

[0016] It may further be provided that after step e), the following steps are performed:

[0017] f) Peeling the cushioning protective foil off the injection-molded part. After carrying out method step f), an injection-molded part is preferably obtained, comprising a base body and an insert foil or sheet, with the tactile layer on the outer side. Unless step f) is carried out, an intermediate product corresponding to the finished injection-molded part is preferably obtained, but with the difference that the cushioning protective foil remains on the tactile layer. This cushioning protective foil then continues to serve as a protective layer for further processing steps or for transporting the intermediate product or injection-molded part to the customer.

[0018] Preferably, the insert film or insert sheet comprises a carrier film, to which the tactile layer is applied. In this case, it is possible that the carrier film ensures the stability of the insert film or insert sheet. However, it is also possible that a supporting layer, in particular a carrier film, is not required, in which case the tactile layer of the insert film or insert sheet is self-supporting.

[0019] The carrier film can comprise a material or a combination of materials selected from the group consisting of polyethylene terephthalate (=PET), polymethyl methacrylate (=PMMA), polycarbonate (=PC), polyethylene (=PE), polyvinyl chloride (=PVC), acrylonitrile butadiene styrene (=ABS), polyurethane (=PU), polybutylene succinate (=PBS), thermoplastic polyurethane (=TPU), polypropylene (=PP), polylactide (=PLA), polyvinyl furanoate (=PEF) and / or polyacrylonitrile (=PAN).

[0020] The insert film or insert sheet can be formed as a multilayer body composed of several layers. In particular, it is provided that the insert film or insert sheet has, in addition to the tactile layer, at least one additional layer or combination of layers selected from the following: an adhesive layer, a decorative layer, a metal layer, a metal oxide layer, a carbon black layer, an adhesion-promoting layer, a primer layer, a color layer, and a functional layer. Preferably, the additional layer is positioned adjacent to the tactile layer or at a distance therefrom.

[0021] The decorative layer can be formed as a single layer or a multi-layer decorative layer. The decorative layer preferably includes one or more layers.

[0022] The decorative layer may preferably comprise one or more color layers, in particular colored varnish layers. These color layers may be variously pigmented and / or transparent and / or opaque, and may also be separated by one or more additional layers, in particular transparent layers. The color layers may be present over the entire surface or only partially within their layer plane. The color layers are preferably applied using known printing methods selected from the group consisting of gravure printing, screen printing, offset printing, inkjet printing, pad printing, xerographic printing, or combinations thereof. The color layer may consist of a binder and at least one component or combination of components selected from the group consisting of colorants, fillers, pigments, optically variable pigments, interference layer pigments, liquid crystal pigments, magnetically orientable pigments, thermochromic pigments, metallic pigments, phosphorescent dyes, and luminescent dyes.

[0023] The decorative layer may also include one or more reflective layers, which are preferably formed as opaque, translucent, and / or partial. In particular, the reflective layer may consist of a metal and / or an HRI layer (HRI = High Refractive Index), thus a layer with a high refractive index, in particular a refractive index greater than 1.5. Examples of metals include aluminum, tin, indium, chromium, silver, gold, or copper, or their alloys. Examples include ZnS or SiO2 as HRI layers.

[0024] Furthermore, the decorative layer may also comprise one or more optically active relief structures, in particular diffractive structures and / or holograms and / or refractive structures and / or matte structures. At least one reflective layer is arranged directly on the relief structure, at least in regions.

[0025] In the case of a metal layer, it is advantageous to apply this metal layer by vapor deposition, physical vapor deposition (PVD) and / or chemical vapor deposition (CVD) and / or sputtering. The different decorative layers can also consist of different metals, in particular metals of different colors.

[0026] The metal layer is preferably applied to the transparent varnish layer or the pigmented varnish layer. Advantageously, an additional varnish layer is then applied to the metal layer as a metal adhesion-promoting layer in order to improve the adhesion of the layers built thereon.

[0027] In particular, the decorative layer may also form one or more patterns. The patterns may be, for example, the outline of a graphical representation, a figurative representation, an image, a visually recognizable design element, a symbol, a logo, a portrait, a pattern, a continuous pattern, alphanumeric characters, a code, a code pattern, a password pattern, text, a color scheme, etc. The patterns may also be individually formed.

[0028] Personalization means, in particular, that the decorative layer includes an item of information that is individually unique for each individual printed product, such as, for example, a unique serial number. Personalization also means, in particular, that the decorative layer includes an item of information that is identical for a group of printed products, but is unique in each case for each group of printed products, such as, for example, a batch number. When the term printing is used hereinafter, this may refer to personalized printing or non-personalized printing.

[0029] The primer preferably includes an adhesive layer and / or an adhesion-promoting layer. The primer layer can be formed to a layer thickness ranging from 1 μm to 5 μm. Materials considered for the primer include PMMA, PVC, polyester, polyurethane, chlorinated polyolefins, polypropylene, epoxy resins, or polyurethane-polyols in combination with deactivated isocyanates. Furthermore, the primer layer may contain inorganic fillers. The primer layer is preferably made of PVC for insert molding or in-mold decoration.

[0030] Preferably, the functional layer is an electrical functional layer, for example in the form of a capacitive element for providing touchpad functionality, resulting in the electrical functional layer being a sensor. Alternatively or additionally, the electrical functional layer may carry at least one light-emitting diode element, for example an organic light-emitting diode ("OLED"). In particular, it is also possible for the electrical functional layer to have a touch function and / or an RFID function. Alternatively or additionally, the electrical functional layer may include electrically conductive lines for providing an electrical connection function and / or a heating function.

[0031] Furthermore, it is preferred that the functional layer have a contact area, preferably in the first zone. It is also possible to provide electrical connection for the component and to include a contact reinforcement in the functional layer, particularly the electrical functional layer, in the first zone. The contact reinforcement facilitates contact between the connecting element and the mating contact. The term "zone" here refers to a defined surface area occupied by the insert film or insert sheet, wherein this surface area lies in a plane formed when viewing the insert film or insert sheet from above. For example, the first zone may completely or only partially occupy the entire surface area of ​​the insert film or insert sheet.

[0032] The functional layer can be used to realize various designs that produce a particularly high-quality optical impression. It is also possible to design the functional layer as a display and / or touch screen.

[0033] The functional layer may also preferably have a soft-touch surface and / or an anti-slip coating.

[0034] Preferably, the tactile layer includes a tactile pattern having ridges and valleys. The tactile pattern can be, for example, a graphically depicted outline, a figurative representation, an image, a visually recognizable design element, a symbol, a logo, a portrait, a pattern, a continuous pattern, alphanumeric characters, a code, a code pattern, a password pattern, text, a color scheme, etc. The tactile pattern can also be personalized.

[0035] It is possible for the elevations to have a height in the range of 10 μm to 100 μm, in particular 20 μm to 50 μm, preferably 25 μm to 35 μm. Furthermore, it is possible for the elevations to have a length and / or width in the range of 0.3 mm to 20 mm, preferably 1 mm to 5 mm. Furthermore, it is preferably provided that the depressions have a width in the range of 0.1 mm to 3 mm, preferably 0.4 mm to 1 mm. These values ​​enable precise tactile feedback and a visually appealing surface texture.

[0036] Furthermore, it is possible that the tactile layer has a pencil hardness of F or better, preferably measured according to ASTM D3363. Figure 6a and Figure 6b The measurement of the pencil hardness is described in detail. A pencil hardness of F or better ensures that the tactile layer is sufficiently scratch-resistant and thus resistant to mechanical environmental influences.

[0037] Preferably, the tactile layer comprises a UV-curable lacquer, preferably comprising a polyurethane acrylate resin. This allows the tactile structure to be applied to the lacquer without requiring significant force, and the tactile structure is then cured using UV radiation. Furthermore, the durability and scratch resistance of the tactile structure are ensured.

[0038] Preferably, the tactile layer is produced or provided by screen printing. Alternatively, it is also possible to pre-cure or fully cure the UV-curable lacquer by means of UV radiation after the molding or stamping of the tactile structure. The tactile structure is preferably molded or stamped into the not-yet-finally-cured UV-curable lacquer by means of a stamping tool, and the tactile layer is cured by irradiation with UV light directly during or after the molding or stamping process. Additional irradiation with UV light may be performed before and / or during the molding or stamping process.

[0039] Preferably, the buffer protection foil has a thickness in the range of 10 μm to 100 μm, preferably 30 μm to 80 μm, and more preferably 50 μm to 70 μm. Such a thickness ensures that the buffer protection foil can be sufficiently compressed so that the underlying tactile structure of the tactile layer is not damaged or deformed by the high pressure and temperature during injection molding, deep drawing, or vacuum forming.

[0040] In particular, the buffering protective foil, preferably the adhesive layer of the buffering protective foil, can have an adhesive force on the tactile layer in the range of from 0.01 N / 25 mm to 1 N / 25 mm, preferably from 0.1 N / 25 mm to 1 N / 25 mm, further preferably from 0.5 N / 25 mm to 1 N / 25 mm. This adhesive force ensures reliable adhesion during processing, preferably during preforming and / or injection molding, and easy removal of the buffering protective foil thereafter.

[0041] It can also be provided that the buffer protection foil has a pressure of from 0.5 N / mm 2 Up to 25 N / mm 2 , preferably from 5 N / mm 2 Up to 25N / mm 2 , further preferably from 5 N / mm 2 Up to 15 N / mm 2 These tensile strength values ​​advantageously ensure that the buffer protection foil can withstand forming forces during deep drawing, vacuum forming or back injection molding.

[0042] Furthermore, the buffer protection foil may have an elongation in the range of 100% to 250%, preferably 100% to 200%, more preferably 100% to 150%. These elongation values ​​ensure that the buffer protection foil has sufficient elasticity during forming, in particular during deep drawing or vacuum forming or back injection molding, and does not tear during forming.

[0043] Furthermore, it is advantageous if the adhesive layer has a thickness in the range from 0.5 to 3 μm, preferably from 1.2 to 1.8 μm, more preferably from 1.5 to 1.8 μm.Preferably, the adhesive layer is provided or produced by means of a slot die.

[0044] Furthermore, it is possible that the adhesive layer has a hardness of Shore A50 or less, preferably measured by using a Shore A hardness tester.

[0045] Preferably, the adhesive layer comprises a pressure-sensitive adhesive with an acrylic component. This ensures a secure bond to the tactile layer, preferably the tactile structure, without permanent adhesion. This means that the cushioning protective foil is easily peelable from the tactile layer, but also has sufficient adhesion to protect the tactile layer (preferably the tactile structure) from deformation during deep drawing, vacuum forming, back injection molding, or other process steps, or during transportation.

[0046] Advantageously, the buffer layer has a thickness in the range of 10 μm to 100 μm, preferably 30 μm to 80 μm, and more preferably 50 μm to 70 μm. Preferably, the buffer layer is thicker before back injection molding than after back injection molding. This is because the buffer layer is compressed during back injection molding due to the prevailing injection pressure of the plastic compound, partially elastically but also plastically. This plastic compression results in the buffer protection foil being thinner after back injection molding than before.

[0047] Furthermore, it may be preferably provided that the buffer layer has a glass transition temperature in the range from 80°C to 110°C, preferably from 85°C to 105°C.

[0048] Advantageously, the buffer layer comprises at least one material or a combination of materials selected from the group consisting of polyvinyl chloride (PVC), polyethylene (PE), and / or polypropylene (PP). Furthermore, it is preferably provided that the buffer layer has a hardness of Shore A 25 or less, preferably measured using a Shore A hardness tester. This ensures that the buffer layer provides a good damping effect during back injection molding. Furthermore, the buffer layer can follow the contours of the tactile structure of the tactile layer. This ensures that the tactile layer or tactile structure is well protected from deformation during back injection molding, deep drawing, and / or vacuum forming.

[0049] Preferably, the application in step b) is carried out by means of a lamination process. This allows the cushioning protective foil to be applied to the tactile layer, in particular the tactile structure, in a cavity-free and contour-following manner.

[0050] Also, the lamination temperature of the lamination process in step b) may range from 30 to 150°C, preferably from 50 to 100°C, more preferably from 60 to 80°C.

[0051] Preferably, the lamination speed of the lamination process in step b) may be in the range of from 1 m / min to 5 m / min, preferably from 1.5 m / min to 4 m / min, more preferably from 2 m / min to 4 m / min.

[0052] Furthermore, the lamination pressure of the lamination process in step b) may be in the range of 10 to 100 bar, preferably 10 to 50 bar, more preferably 30 to 50 bar. This pressure ensures that the cushioning foil is applied in such a way that it follows the contours of the tactile layer.

[0053] Furthermore, it is possible that after step b), in particular before step c), the following steps are further performed:

[0054] b1) Deep drawing or vacuum forming the insert foil or insert sheet together with the applied buffer protection foil.

[0055] This allows the insert sheet or film to be preformed before back injection molding. Preferably, the insert sheet or film already assumes the final shape of the injection-molded part, preventing further deformation of the insert sheet or film during back injection molding in the injection molding machine. As explained above, the cushioning protective foil is preferably designed to easily withstand the forming forces in step b1).

[0056] Preferably, the deep drawing or vacuum forming in step b1) is performed at a deep drawing temperature or vacuum forming temperature ranging from 50° C. to 300° C., preferably from 90° C. to 200° C., more preferably from 120° C. to 150° C. This temperature ensures that the insert sheet or insert film together with the buffer protection foil becomes sufficiently stretchable for forming while retaining the tactile structure of the tactile layer.

[0057] It can also be provided that the back injection molding in step d) has an injection temperature in the range of from 100° C. to 500° C., preferably from 180° C. to 400° C., more preferably from 200° C. to 300° C. Furthermore, it is possible that the back injection molding in step d) has an injection pressure in the range of from 800 bar to 1300 bar.

[0058] Advantageously, the injection-molded part, in particular the base body, and / or the plastic compound comprises a plastic material including a thermoplastic, in particular an impact-resistant thermoplastic. Furthermore, the plastic material particularly comprises polyethylene (PE), polycarbonate (PC), polypropylene (PP), polystyrene (PS), polybutadiene, polynitrile, polyester, polyurethane, polymethacrylate, polyacrylate, polyamide, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), preferably acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), ABS-PC, PET-PC, PBT-PC, PC-PBT, and / or ASA-PC, and / or copolymers or mixtures thereof. It is also possible for the plastic material to contain inorganic or organic fillers, preferably SiO2, Al2O3, TiO2, clay minerals, silicates, zeolites, glass fibers, carbon fibers, glass beads, organic fibers, or mixtures thereof. Fillers are particularly added to the plastic material to further increase the stability of the injection-molded part, in particular the base body. Furthermore, these fillers can reduce the proportion of polymer material, thereby reducing the production costs and / or weight of the injection-molded component, in particular the base body. It is also possible for the plastic material to contain inorganic or organic auxiliary substances, which in particular improve the processability of the plastic material. Furthermore, the plastic material can be biodegradable and / or compostable. For example, the plastic material can include polylactide (PLA) or polylactic acid.

[0059] Furthermore, it is preferably provided that during and / or after step d), the deformation of the elevations of the haptic structure is less than 10%, in particular less than 5%, relative to the height of the elevations.

[0060] Comparative tests were carried out to determine the deformation of the tactile layer, preferably the tactile structure, during back injection molding in an injection molding machine with and without a buffer protection foil.For this purpose, two different embodiments of the insert film were tested.

[0061] The first example is an insert film with a single tactile structure in the form of a three-pointed star as the tactile layer. The tactile layer has a pencil hardness of F and comprises a UV-curable lacquer containing 100% solids content in a polyurethane acrylate resin. The three-pointed star is configured as a single protrusion of the tactile structure. The height of the three-pointed star is 32µm ± 1µm. In each of the other two spatial dimensions, the dimensions of the three-pointed star are 600µm ± 5µm. These values ​​for the tactile structure are before back injection molding. This insert film is then back injection molded in an injection molding machine without a buffering protective foil, and the dimensions of the tactile structure or three-pointed star are then measured. After back injection molding, the height of the tactile structure or three-pointed star is 22µm ± 1µm. However, the dimensions in the other two spatial directions remain virtually unchanged. The same insert film with the same tactile structure is also back injection molded, but this time, a buffering protective foil is applied to the tactile layer or tactile structure of the insert film before back injection molding. The buffer foil used consists of a buffer layer and an adhesive layer. The buffer layer has a thickness of 80 μm ± 2 μm and a Shore A hardness of <25. The adhesive layer has a thickness of 1.5 μm ± 0.3 μm and a Shore A hardness of <50. The insert film with the buffer foil applied is then placed in an injection molding machine, with the foil in contact with one wall of the injection mold, and then back-injected with a plastic compound. The plastic compound is injected at an injection pressure of 1300 bar and an injection speed of 65 m / s. The injection temperature of the plastic compound ranges from 250°C to 270°C. Furthermore, the injection time ranges from 2 to 4 seconds, and the cooling time ranges from 15 to 20 seconds, with a cooling temperature of 45°C. Finally, the injection-molded part is removed from the mold, the buffer foil is released, and the dimensions of the tactile structure or three-pointed star are measured. This results in a height of 30.5 μm ± 1 μm. The dimensions in the other two spatial directions remain unchanged.

[0062] In a second embodiment, a large-area continuous pattern was tested as a tactile structure for the embedded film. The parameters regarding the layer thickness, layer structure, and hardness of the tactile layer and the buffer protection foil were the same as in the first embodiment. The tactile structure was a grid with a plurality of equally sized squares with a side length of 5 mm. The protuberances of the tactile structure were square grid lines with a height of 22 µm and a width of 344 µm. For back injection molding of the embedded film without the buffer protection foil, the tactile structure or grid had a height of 2 μm and a width of 417 μm after back injection molding. For back injection molding of the embedded film with the buffer protection foil, the tactile structure had a height of 20 µm and a constant width of 344 µm after back injection molding.

[0063] For a better overview, the results of the comparative tests are shown in the table below.

[0064] These comparative tests therefore clearly show that the deformation of the haptic layer or haptic structure is significantly reduced when using a buffering protection foil compared to back injection molding without a buffering protection foil as known in the prior art.

[0065] For the above two embodiments, for the variant with the buffer protection foil, the adhesion of the buffer protection foil on the tactile layer was also measured before and shortly after the back injection molding and several days after the back injection molding. For this reason, several samples with a length of 20 cm and a width of 2.5 cm were prepared. Therefore, the measurement before the back injection molding only involves the embedded foil with the buffer protection foil applied thereto, and the measurement after the back injection molding involves the injection molded part with the buffer protection foil. The sample is attached to the aluminum plate with strong double-sided tape so that the buffer protection foil faces away from the aluminum plate. Moreover, the sample is pressed onto the aluminum plate with a roller. The prepared aluminum plate is then placed in a ZwickRoell GmbH & Co.KG model Z005 testing machine. Then one end of the buffer protection foil is attached to the testing device of the testing machine, and finally the buffer foil is pulled away from the embedded foil or from the injection molded part via the testing device, and the required force is determined. Determine the adhesion shown in the table below.

[0066] The adhesion force determined during this process ensures that the cushioning foil is firmly bonded to the tactile layer, protecting the tactile structure from deformation. Furthermore, the adhesion force determined is low enough that the cushioning foil can be removed from the tactile layer without leaving any residue and without requiring excessive force.

[0067] The present invention is used wherever a tactile surface of an injection-molded part is required. This can be found, for example, in the automotive sector, particularly for cockpit components, panels, armatures, etc. Furthermore, the present invention is also suitable for use in household appliances, particularly for control and operating panels, covers, housings, etc.

[0068] Further embodiments of the present invention are shown in the drawings and described below. Therefore, the embodiments shown should not be understood as limiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figures 1a to 1c shows the process of back injection of an embedded film with a tactile structure according to the prior art;

[0070] Figure 2 shows a schematic representation of a method for producing an injection-molded part;

[0071] Figures 3a to 3f a schematic representation showing in detail the steps of a method for producing an injection-molded part;

[0072] Figure 4 A schematic representation of the intermediate product is shown;

[0073] Figure 5 A schematic representation of an injection molded part is shown;

[0074] Figures 6a to 6b A schematic representation of the pencil hardness test is shown. DETAILED DESCRIPTION

[0075] The accompanying drawings illustrate various examples of embodiments of the present invention. Components with identical or similar functions are provided with the same reference numerals in each case. Where the embodiments shown in the drawings have similarities, these similarities are not described more than once to avoid repetition. The respective differences between the embodiments are described with respect to the drawings. It goes without saying that those skilled in the art may modify the various embodiments or combine features of these embodiments within the scope of the claims.

[0076] Figures 1a to 1c A method of back-injecting the insert film 100 with a plastic compound is shown, whereby the insert film 100 has a tactile structure, as is known in the art. Figure 1a As shown in FIG, an insert film 100 having a tactile structure is first provided. The insert film 100 is then placed in an injection mold 110 of an injection molding machine so that the tactile structure directly abuts against the wall of the cavity of the injection mold 110, as shown in FIG. Figure 1b The embedded film 100 is then back-injected with a molten plastic compound and removed from the injection mold 110. The finished injection molded part 120 according to the prior art is Figure 1c . However, in the prior art, the haptic structure of the embedded film 100 is deformed or compressed due to the high pressure and thermal shock during back injection molding in the injection molding machine. In other words, in the prior art process, the haptic structure loses height due to back injection molding. Therefore, in the prior art, an injection-molded part 120 having a deformed haptic structure is provided.

[0077] Figure 2 A schematic representation of a method for producing an injection molded part 50 is shown. Figure 2 In the method shown, the following steps are performed:

[0078] a) providing an insert film or insert sheet 10, wherein the insert film or insert sheet 10 comprises a tactile layer 11;

[0079] b) applying a buffer protective film comprising an adhesive layer 21 and a buffer layer 22 to the tactile layer 11 of the insert film or insert sheet 10;

[0080] c) inserting the insert film or insert sheet 10 into an injection mold 60 of an injection molding machine so that the buffer protection foil 20 is in contact with the wall of the injection mold 60;

[0081] d) back injection molding the insert film or insert sheet 10 with a plastic compound to provide an injection molded part 50;

[0082] e) Removing the injection-moulded part 50 from the injection mould 60 .

[0083] Preferably, if Figure 2 , this method is used to provide an intermediate product 40 which substantially corresponds to the final injection-molded part 50 and further comprises a buffer protection foil 20. The buffer protection foil 20 then serves as a protective layer for further processing steps or for transport.

[0084] In an alternative embodiment, it is possible that after step e) the following steps are performed:

[0085] f) Peeling off the cushioning protection foil 20 of the injection-molded part 50 .

[0086] After carrying out method step f), an injection-molded component 50 is preferably obtained which comprises the base body 30 and the insert foil or insert sheet, with the tactile layer 11 on the outer side.

[0087] Figures 3a to 3f Schematic details of a method for producing an injection-molded part 50 are shown.

[0088] Figure 3a First, method step a) is shown, namely providing an insert film or insert sheet 10, whereby Figure 3a The embodiment of the present invention is an insert film 10. The insert film 10 includes a tactile layer 11. In this case, the tactile layer 11 is a self-supporting layer and is therefore the only layer of the insert film 10. However, in alternative embodiments, the insert film or insert sheet 10 may include a carrier film to which the tactile layer 11 is applied. In this case, the carrier film ensures the stability of the insert film or insert sheet 10.

[0089] As in Figure 3aAs can be seen in the figure, the tactile layer 11 includes a tactile pattern with elevations and depressions. The elevations and depressions ensure that a tactile effect is generated. In particular, it is provided that the elevations have a height in the range of 10 μm to 100 μm, in particular from 20 μm to 50 μm, preferably from 25 μm to 35 μm. Correspondingly, the depressions preferably have a depth in the range of 10 μm to 100 μm, in particular from 20 μm to 50 μm, preferably from 25 μm to 35 μm. Such height and depth ensure that the elevations and depressions are tactilely perceptible. It is also possible that the elevations have a length and / or width in the range of 0.3 mm to 20 mm, preferably from 1 mm to 5 mm. Furthermore, the depressions can have a width in the range of 0.1 mm to 3 mm, preferably from 0.4 mm to 1 mm. Advantageously, the elevations and depressions form a pattern.

[0090] Possibly, the tactile layer 11 may comprise a UV-curable lacquer, preferably with a polyurethane acrylate resin. Furthermore, the tactile layer 11 may be produced or applied by means of screen printing.

[0091] It is particularly provided that the tactile layer 11 has a pencil hardness of F or better, preferably measured according to ASTM D 3363. The pencil hardness test is described in detail with respect to FIG.

[0092] exist Figure 3b In FIG, method step b) is shown, namely applying a buffer protection foil 20 to the tactile layer 11 of the insert film or insert sheet 10. Figure 3b As can be seen in FIG, the buffering protective foil 20 includes an adhesive layer 21 and a buffering layer 22. Preferably, the buffering protective foil 20 is applied so that the adhesive layer 21 is positioned directly adjacent to the tactile layer 11. Preferably, the adhesive layer 21 ensures sufficient adhesion to the tactile layer 11, the adhesion being large enough to withstand the effects of injection molding and transportation, but small enough to allow the buffering protective foil 20 to be easily removed from the tactile layer 11. In particular, the buffering protective foil 20, preferably the adhesive layer 21 of the buffering protective foil 20, has an adhesion on the tactile layer 11 in the range of from 0.01 N / 25 mm to 1 N / 25 mm, preferably from 0.1 N / 25 mm to 1 N / 25 mm, and further preferably from 0.5 N / 25 mm to 1 N / 25 mm.

[0093] Preferably, the adhesive layer 21 has a thickness ranging from 0.5 μm to 3 μm, preferably from 1.2 μm to 1.8 μm, more preferably from 1.5 μm to 1.8 μm.

[0094] It is possible that the adhesive layer 21 has a hardness of Shore A50 or less, preferably measured by using a Shore A hardness tester.

[0095] In particular, the adhesive layer 21 comprises a pressure-sensitive adhesive having an acrylic component. Preferably, the adhesive layer 21 is applied to the buffer layer 22 by means of a slot die.

[0096] Preferably, adhesive layer 21 is required because the application in step b) is advantageously performed by means of a lamination process. The lamination temperature in step b) may range from 30°C to 150°C, preferably from 50°C to 100°C, and more preferably from 60°C to 80°C. Furthermore, the lamination speed in step b) may range from 1 m / min to 5 m / min, preferably from 1.5 m / min to 4 m / min, and more preferably from 2 m / min to 4 m / min. Furthermore, the lamination pressure in step b) may range from 10 bar to 100 bar, preferably from 10 bar to 50 bar, and more preferably from 30 bar to 50 bar.

[0097] Furthermore, it is preferred that the thickness of the buffer layer 22 be in the range of 10 μm to 100 μm, preferably 30 μm to 80 μm, more preferably 50 μm to 70 μm, in particular before back injection. Furthermore, it is possible that the buffer layer 22 may have a glass transition temperature in the range of 80° C. to 110° C., preferably 85° C. to 105° C.

[0098] Advantageously, the buffer layer 22 may comprise at least one material or a combination of materials selected from the group consisting of polyvinyl chloride (PVC), polyethylene (PE), and / or polypropylene (PP). Preferably, the buffer layer 22 has a hardness of Shore A 25 or less, preferably measured using a Shore A hardness tester.

[0099] The buffer layer 22 as part of the buffer protection foil 20 acts as a damping layer during back injection molding of the insert film or insert sheet 10 so that the tactile structure is not deformed at all or deformed less than in the prior art by the pressure during injection molding.

[0100] After applying the buffer protection foil 20 to the insert film or insert sheet 10 in step b), the following steps (not shown in the figure) may be performed:

[0101] b1) Deep drawing or vacuum forming the inlay foil or inlay sheet together with the applied buffer protection foil 20 .

[0102] Preferably, step b1) is performed after step b) and before step c).

[0103] The deep drawing or vacuum forming of the insert film or insert sheet 10 in step b1) is preferably used to initially preform the insert film or insert sheet 10 so that the subsequent back injection molding can directly follow the contour of the insert film or insert sheet 10. This ensures that the insert film or insert sheet is no longer deformed in the injection mold 60, and thus a high-quality injection-molded part 50 can be provided.

[0104] Advantageously, the deep drawing or vacuum forming in step b1) is performed at a deep drawing temperature or vacuum forming temperature ranging from 50 to 300°C, preferably from 90 to 200°C, more preferably from 120 to 150°C.

[0105] Preferably, the buffer protection foil 20 is designed to withstand the strong deformation that sometimes occurs during deep drawing or vacuum forming without causing wrinkling or cracking. In this case, it is preferably provided that the buffer protection foil 20 has an elongation in the range of 100% to 250%, preferably 100% to 200%, and more preferably 100% to 150%. This is preferably achieved by selecting the material of the buffer layer 22. As mentioned above, preferred materials for the buffer layer 22 are PVC, PE, or PP.

[0106] Next, as in Figure 3c As can be seen in FIG, according to method step c), the insert film or insert sheet 10 is inserted into the injection mold 60 of the injection molding machine so that the buffer protection foil 20 is in contact with the wall of the injection mold 60. Figure 3c As can be seen in the figure, the insert film or insert sheet 10 is a flat, planar insert film or insert sheet 10. This means that the insert film or insert sheet 10 has not been deep-drawn or vacuum-formed. As described above, in advantageous embodiments, it can be provided that the insert film or insert sheet 10 is preformed, in particular by deep-drawing or vacuum-forming. In this case, the preformed insert film or insert sheet 10 is then inserted into the injection mold 60 of the injection molding machine.

[0107] Moreover, in Figure 3c : The height x of the buffer protection foil 20 is shown in FIG. X represents the height of the buffer protection foil before back injection molding.

[0108] Later, as in Figure 3d As can be seen in FIG, according to method step d), the insert film or insert sheet 10 is back-injection molded with a plastic compound. Preferably, the back-injection molding is performed at an injection temperature ranging from 100° C. to 500° C., preferably from 180° C. to 400° C., and more preferably from 200° C. to 300° C. In addition, the back-injection molding in step d) can have an injection pressure ranging from 800 bar to 1300 bar.

[0109] The plastic compound then forms the base 30 of the subsequently injection-molded component 50 and is bonded to the side of the insert film or insert sheet 10 facing away from the buffer protection foil 20. During back injection molding, the buffer protection foil 20 is elastically and plastically compressed due to the thermal effects and injection pressure during injection molding. This is caused by Figure 3d The height y of the buffer protection foil 20 is indicated. Figure 3c Compared to the height x of the bumper protection foil 20 in the back injection molding, or before back injection molding, the height y is lower than the height x due to the compression of the bumper protection foil 20. The compression of the bumper protection foil 20 prevents deformation or compression of the tactile structure of the tactile layer 11 of the inlay film or inlay sheet 10. However, slight deformation or compression of the tactile structure may still occur. Preferably, the deformation relative to the height of the protuberance is less than 10%, particularly less than 5%. However, this deformation is significantly less than that known in the prior art.

[0110] Figure 3e Method step e) is now shown, namely the removal of the injection molded part 50 from the injection mold 60. However, since the injection molded part 50 still comprises the buffer protection foil 20, the injection molded part 50 serves as an intermediate product 40. Figure 4 Further details of the intermediate product 40 are described. This intermediate product 40 can either be processed immediately or shipped to the customer first. The buffer protection foil 20 preferably remains on the injection molded part 50. In this way, the buffer protection foil 20 continues to serve as a protection against external environmental influences.

[0111] at last, Figure 3f Process step f) is shown, i.e. peeling off the buffer protection foil 20. The final injection-molded part 50 is thereby obtained or provided. Figure 5 Further details of the intermediate product 40 are described.

[0112] Figure 4 A schematic diagram of an intermediate product 40 is shown, for example Figure 3e As shown in . Figure 4 The intermediate product 40 comprises a base body 30 formed of a plastic compound, a tactile layer 11 fixedly connected to the base body 30 and a releasable cushioning protective foil 20 adjacent to the tactile layer 11. Figure 4 The buffer protection foil 20 includes an adhesive layer 21 and a buffer layer 22 , wherein the buffer layer 22 represents an outer layer of the intermediate product 40 .

[0113] Preferably, the buffer protection foil 20 has a thickness ranging from 10 μm to 100 μm, preferably from 30 μm to 80 μm, further preferably from 50 μm to 70 μm.

[0114] Furthermore, it is possible that the buffering protection foil 20 may have an adhesive force on the tactile layer 11 in the range of 0.01 N / 25 mm to 1 N / 25 mm, preferably 0.1 N / 25 mm to 1 N / 25 mm, further preferably 0.5 N / 25 mm to 1 N / 25 mm. This adhesive force ensures that the buffering protection foil 20 has sufficient adhesion so that the buffering foil does not come loose during transportation or further processing, but is still easy enough to remove from the tactile layer 11.

[0115] Figure 5 For example, it is shown that Figure 3f Schematic diagram of an injection molded part 50 is shown in FIG. Figure 5 The injection-molded component 50 comprises a base body 30 consisting of a plastic compound and a tactile layer 11 fixedly connected to the base body 30. Preferably, the tactile layer 11 is part of an insert film or insert sheet 10. In alternative embodiments, it is possible that the injection-molded component 50 comprises a base body 30 consisting of a plastic compound and an insert film or insert sheet 10, wherein the insert film or insert sheet 10 is fixedly connected to the base body 30, and wherein the insert film or insert sheet 10 comprises the tactile layer 11. In each embodiment of the injection-molded component 50, it is preferably provided that the tactile layer 11 represents the outer layer of the injection-molded component 50. This ensures that the tactile structure of the tactile layer 11 can also be perceived by touch.

[0116] Preferably, the tactile layer 11 includes a tactile pattern with elevations and depressions. The elevations may have a height in the range of 10 μm to 100 μm, in particular 20 μm to 50 μm, preferably 25 μm to 35 μm. Furthermore, it is preferably provided that the elevations have a length and / or width in the range of 0.3 mm to 20 mm, preferably 1 mm to 5 mm. Furthermore, the depressions may have a width in the range of 0.1 mm to 3 mm, preferably 0.4 mm to 1 mm.

[0117] Preferably, the tactile layer 11 comprises a UV-curable lacquer, preferably with a polyurethane acrylate resin.

[0118] It is preferably provided that the tactile layer 11 has a pencil hardness of F or better, preferably measured according to ASTM D3363.

[0119] Pencil hardness test Figure 6a and Figure 6bSchematically shown in FIG. The pencil hardness was measured using an electric pencil hardness tester with the model name A-3086*1 from Tianjin Jin Fu Lun Technology Corporation. The test was carried out at a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. Pencils 300 with the model name "Uni" of Mitsubishi Pencil Company Limited of various hardness grades, such as F, 6B, etc., were used. For the test, a cylindrical pencil lead containing graphite was extended 5 to 6 cm outside the pencil 300. The pencil was then ground at an angle of 90° on sandpaper 310 until the pencil tip was flat, as shown in FIG. Figure 6a shown.

[0120] Then, the pencil 300 is positioned at an angle of 45° and pushed forward 5-6 cm along the surface of the tactile layer 11 of the injection molded part 50, as in Figure 6b The contact load applied to the surface of the tactile layer 11 corresponds to an equivalent of 500 grams.

[0121] To determine the pencil hardness of the tactile layer 11, different pencil hardnesses are tested one after another. The surface of the tactile layer 11 is checked for scratches. If no scratches are found, the tactile layer 11 has passed the test for the corresponding pencil hardness. Testing is performed with increasingly harder pencil hardnesses until a scratch appears on the surface of the tactile layer 11. The test immediately preceding the scratch-inducing test then determines the pencil hardness of the tactile layer 11. For example, if the pencil hardness of the tactile layer 11 is designated as 4H, testing with a 4H pencil 300 will not cause any scratches on the surface, but testing with a 5H pencil 300 will cause scratches on the surface.

[0122] Reference Signs List

[0123] 10 Embedding film or embedding sheet

[0124] 11 Tactile Layer

[0125] 20 Buffer protection foil

[0126] 21 Adhesive layer

[0127] 22 Buffer layer

[0128] 30 matrix

[0129] 40 Intermediate products

[0130] 50 injection molded parts

[0131] 60 Injection mold

[0132] 100 Embedded membrane according to prior art

[0133] 110 Injection mold according to the prior art

[0134] 120 According to the prior art substrate

[0135] 200 Injection molded parts according to the prior art

[0136] 300 pencils

[0137] 310 sandpaper

[0138] x Height of the cushioning protection foil before injection molding

[0139] y Height of the cushioning protection foil after injection molding.

Claims

1. A method for producing an injection-molded part (50), wherein: In particular, perform the following steps in the following order: a) providing an insert film or insert sheet, wherein the insert film or insert sheet (10) comprises a tactile layer (11); b) applying a buffer protective film comprising an adhesive layer (21) and a buffer layer (22) onto the tactile layer (11) of the insert film or insert sheet (10); c) inserting the insert film or insert sheet (10) into an injection mold (60) of an injection molding machine so that the buffer protection foil (20) is in contact with a wall of the injection mold (60); d) back injection molding the insert film or insert sheet (10) with a plastic compound to provide an injection molded part (50); e) Removing the injection molded part (50) from the injection mold (60).

2. The method according to claim 1, It is characterized by After step e), the following steps are performed: f) peeling off the buffer protection foil (20) of the injection molded part (50).

3. The method according to claim 1 or 2, It is characterized by The inlay film or inlay sheet (10) comprises a carrier film to which the tactile layer (11) is applied.

4. The method according to claim 1 , It is characterized by The tactile layer (11) comprises a tactile pattern having ridges and valleys.

5. The method according to claim 4, It is characterized by The elevations have a height in the range from 10 μm to 100 μm, in particular from 20 μm to 50 μm, preferably from 25 μm to 35 μm.

6. The method according to claim 4 or 5, It is characterized by The protuberances have a length and / or width in the range from 0.3 mm to 20 mm, preferably 1 mm to 5 mm.

7. The method according to claim 4 , It is characterized by The recess has a width in the range from 0.1 mm to 3 mm, preferably from 0.4 mm to 1 mm.

8. The method according to one of claims 1 to 7, It is characterized by The tactile layer (11) has a pencil hardness of F or better, preferably measured according to ASTM D3363.

9. The method according to one of claims 1 to 8, It is characterized by The tactile layer (11) comprises a UV-curable lacquer, preferably comprising a polyurethane acrylate resin.

10. The method according to one of claims 1 to 9, It is characterized by The buffer protection foil (20) has a thickness ranging from 10 μm to 100 μm, preferably from 30 μm to 80 μm, further preferably from 50 μm to 70 μm.

11. The method according to one of claims 1 to 10, It is characterized by The buffer protection foil (20), preferably the adhesive layer (21) of the buffer protection foil (20), has an adhesion force on the tactile layer (11) in the range of from 0.01 N / 25mm to 1 N / 25mm, preferably from 0.1 N / 25mm to 1 N / 25mm, further preferably from 0.5 N / 25mm to 1 N / 25mm.

12. The method according to claim 1 , It is characterized by The buffer protection foil (20) has a pressure of from 0.5 N / mm 2 Up to 25 N / mm 2 , preferably from 5 N / mm 2 Up to 25 N / mm 2 , further preferably from 5 N / mm 2 Up to 15 N / mm 2 Tensile strength within the range.

13. The method according to one of claims 1 to 12, It is characterized by The buffer protection foil (20) has an elongation in the range of from 100% to 250%, preferably from 100% to 200%, more preferably from 100% to 150%.

14. The method according to one of claims 1 to 13, It is characterized by The adhesive layer (21) has a thickness ranging from 0.5 μm to 3 μm, preferably from 1.2 μm to 1.8 μm, more preferably from 1.5 μm to 1.8 μm.

15. The method according to one of claims 1 to 14, It is characterized by The adhesive layer (21) has a hardness of Shore A50 or less, preferably measured by using a Shore A hardness tester.

16. The method according to one of claims 1 to 15, It is characterized by The adhesive layer (21) comprises a pressure-sensitive adhesive having an acrylic component.

17. The method according to one of claims 1 to 16, It is characterized by The buffer layer (22) has a thickness ranging from 10 μm to 100 μm, preferably from 30 μm to 80 μm, more preferably from 50 μm to 70 μm.

18. The method according to one of claims 1 to 17, It is characterized by The buffer layer (22) has a glass transition temperature in the range of from 80°C to 110°C, preferably from 85°C to 105°C.

19. The method according to one of claims 1 to 18, It is characterized by The buffer layer (22) comprises at least one material or a combination of materials selected from the group consisting of polyvinyl chloride (=PVC), polyethylene (=PE) and / or polypropylene (=PP).

20. The method according to one of claims 1 to 19, It is characterized by The buffer layer (22) has a hardness of Shore A 25 or less, preferably measured using a Shore A hardness tester.

21. The method according to one of claims 1 to 20, It is characterized by The application in step b) is carried out by means of a lamination process.

22. The method according to claim 21, It is characterized by The lamination temperature of the lamination process in step b) is in the range of from 30 to 150°C, preferably from 50 to 100°C, more preferably from 60 to 80°C.

23. The method according to claim 21 or 22, It is characterized by The lamination speed of the lamination process in step b) is in the range of from 1 m / min to 5 m / min, preferably from 1.5 m / min to 4 m / min, more preferably from 2 m / min to 4 m / min.

24. The method according to one of claims 21 to 23, It is characterized by The lamination pressure of the lamination process in step b) is in the range of from 10 bar to 100 bar, preferably from 10 bar to 50 bar, more preferably from 30 bar to 50 bar.

25. The method according to one of claims 1 to 24, It is characterized by After step b), and in particular before step c), the following steps are further performed: b1) Deep drawing or vacuum forming the embedding foil or embedding sheet together with the applied buffer protection foil (20).

26. The method according to claim 25, It is characterized by The deep drawing or vacuum forming in step b1) is performed at a deep drawing temperature or vacuum forming temperature ranging from 50 to 300°C, preferably from 90 to 200°C, more preferably from 120 to 150°C.

27. The method according to one of claims 1 to 26, It is characterized by The back injection molding in step d) has an injection temperature ranging from 100 to 500°C, preferably from 180 to 400°C, more preferably from 200 to 300°C.

28. The method according to one of claims 1 to 27, It is characterized by The back injection molding in step d) has an injection pressure in the range from 800 bar to 1300 bar.

29. The method according to one of claims 1 to 28, It is characterized by During and / or after step d), the deformation of the elevations of the tactile structure is less than 10%, in particular less than 5%, relative to the height of the elevations.

30. Injection-molded part (50), in particular an injection-molded part produced by a method according to one of claims 1 to 29, in, The injection-molded component (50) comprises a base body (30) consisting of a plastic compound and a tactile layer (11) fixedly connected to the base body (30).

31. The injection-molded part (50) according to claim 30, It is characterized by The tactile layer (11) comprises a tactile pattern having ridges and valleys.

32. The injection-molded part (50) according to claim 31, It is characterized by The elevations have a height in the range from 10 μm to 100 μm, in particular from 20 μm to 50 μm, preferably from 25 μm to 35 μm.

33. The injection-molded part (50) according to claim 30 or 31, It is characterized by The protuberances have a length and / or width in the range from 0.3 mm to 20 mm, preferably 1 mm to 5 mm.

34. Injection-molded part (50) according to one of claims 31 to 33, It is characterized by The recess has a width in the range from 0.1 mm to 3 mm, preferably from 0.4 mm to 1 mm.

35. Injection-molded part (50) according to one of claims 30 to 34, It is characterized by The tactile layer (11) has a pencil hardness of F or better, preferably measured according to ASTM D3363.

36. Injection-molded part (50) according to one of claims 30 to 35, It is characterized by The tactile layer (11) comprises a UV-curable lacquer, preferably comprising a polyurethane acrylate resin.

37. An intermediate product (40) comprising an injection-moulded part (50) according to one of claims 30 to 36, preferably produced by a method according to one of claims 1 to 29, It is characterized by The intermediate product (40) further comprises a releasable cushioning protection foil (20) adjacent to the tactile layer (11), wherein the cushioning protection foil (20) comprises an adhesive layer (21) and a cushioning layer (22).

38. The intermediate product (40) according to claim 37, It is characterized by The buffer protection foil (20) has a thickness ranging from 10 μm to 100 μm, preferably from 30 μm to 80 μm, further preferably from 50 μm to 70 μm.

39. The intermediate product (40) according to claim 37 or 38, It is characterized by The buffer protection foil (20) has an adhesive force on the tactile layer (11) in the range of from 0.01 N / 25mm to 1 N / 25mm, preferably from 0.1 N / 25mm to 1 N / 25mm, further preferably from 0.5 N / 25mm to 1 N / 25mm.

40. The intermediate product (40) according to one of claims 37 to 39, It is characterized by The adhesive layer (21) has a thickness ranging from 0.5 μm to 3 μm, preferably from 1.2 μm to 1.8 μm, more preferably from 1.5 μm to 1.8 μm.

41. The intermediate product (40) according to one of claims 37 to 40, It is characterized by The adhesive layer (21) has a hardness of Shore A50 or less, preferably measured by using a Shore A hardness tester.

42. The intermediate product (40) according to one of claims 37 to 41, It is characterized by The adhesive layer (21) comprises a pressure-sensitive adhesive having an acrylic component.

43. The intermediate product (40) according to one of claims 37 to 42, It is characterized by The buffer layer (22) has a thickness ranging from 10 μm to 100 μm, preferably from 30 μm to 80 μm, more preferably from 50 μm to 70 μm.

44. The intermediate product (40) according to one of claims 37 to 43, It is characterized by The buffer layer (22) comprises at least one material or a combination of materials selected from the group consisting of polyvinyl chloride (=PVC), polyethylene (=PE) and / or polypropylene (=PP).

45. The intermediate product (40) according to one of claims 37 to 44, It is characterized by The buffer layer (22) has a hardness of Shore A 25 or less, preferably measured using a Shore A hardness tester.

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