FILM LAMINATE AND INTERIOR CLADDING PART FOR MOTOR VEHICLES

Description

[0001] The invention relates to a film laminate comprising at least one or more layers of extruded decorative material with a lacquer layer on the top side and a foam layer on the bottom side. The invention further relates to interior trim parts of motor vehicles that are provided with such a film laminate.

[0002] In the field of decorative film laminates for automotive interiors, essentially two constructions are currently used.

[0003] For applications and components where the film laminate is subjected to significant stretching (e.g., up to 300%) in downstream thermal forming processes, compact film constructions, which can be composed of several layers, are preferred. Such compact films based on polyolefins are described, for example, in DE 10018196 A1. DE 10 2011 053224 A1 also describes a film laminate for use as an interior trim component of a motor vehicle. In the production of an interior trim component of a motor vehicle, such as an instrument panel, the film construction is first thermoformed using a positive or negative thermoforming process. Subsequently, in a second processing step, the resulting "skin" is back-foamed with a typically PUR-based foam, and this foam is bonded to a stable substrate.

[0004] For applications and components where the film laminate undergoes slight stretching (e.g., < 200%) in downstream thermal forming processes, film laminates with at least one foamed layer, so-called foam film laminates, can be used. These consist of a single or multi-layered decorative layer with a lacquer coating on the top and a polyolefin-based foam layer on the bottom. Such film laminates are mentioned at the beginning. In the production of an interior trim part for a motor vehicle, such as an instrument panel, the entire foam film laminate is first thermoformed using a positive or negative thermoforming process. The resulting "foam skin" is then bonded to the stable substrate using an adhesive.The advantage of these second type of foam laminates lies in the fact that they can be processed in a single-stage process into a shaped, foamed component with the desired softness (desired feel) imparted by the foam. With the first type of compact film construction, this can only be achieved with a back-foaming process following thermoforming.

[0005] The film laminates are used to produce components for automotive interiors, including instrument panels, using thermoforming processes. When film laminates are used in components containing airbags, they must exhibit the required tear behavior, ensuring that the airbag deploys within defined timeframes, preventing particle ejection and guaranteeing passenger protection. To achieve this, current technology typically involves weakening the back of the foam film laminate (a predetermined breaking point), usually by laser cutting. These predetermined breaking points (weakening lines) are either visible immediately after application or become visible during subsequent use of the component. This visibility has been perceived as a significant visual defect.Furthermore, additional costs are incurred for the procurement and operation of the machines for the application of the weakening lines, which is why foam film laminates have so far only been used to a limited extent for components with airbag function.

[0006] Foil laminates comprising at least one or more layers of extruded decorative material with a lacquer layer on the top and a foam layer on the bottom, suitable for dashboards and designed to function without additional weakening lines, are known from EP 2 117 881 B1 and WO 2016 / 008613 A1. EP 2 117 881 B1 specifies that the top layer (decorative layer) is to be at least two layers thick, with an outer and an inner layer. The inner layer and the foam layer exhibit an elongation at break that is significantly lower than that of the outer layer of the decorative material. Furthermore, the inner layer is disclosed to have higher values ​​for elongation at break in the longitudinal direction than in the transverse direction. However, it has been shown that the foil laminates mentioned in EP 2 117 881 B1 could not be used for all airbag flap geometries without the need to incorporate additional weakening lines.Furthermore, the presence of the inner layer with low elongation at break within the decorative layer sometimes led to poorer deep-drawing behavior with a poorer grain pattern.

[0007] The invention is based on the objective of providing a film laminate that can be used as an interior trim component in motor vehicles, particularly in the area of ​​airbag covers, and that does not require weak lines. At the same time, the film laminate should be suitable for thermoforming processes, meaning that it should exhibit sufficient stability for thermal forming processes with a degree of stretching of up to 200%.

[0008] The problem is solved by a film laminate of claim 1. Additional features result from the dependent claims.

[0009] During airbag deployment, the so-called airbag discharge, after the decorative layer initially breaks, the layer tears further in the longitudinal direction of the extruded film's manufacturing direction. This is then followed by a transverse tear, which opens, for example, a rectangular airbag flap. With conventional film laminates, the tearing forces are lower in the longitudinal direction than in the transverse direction due to the anisotropy caused by the film's extrusion, making a contour-conforming tear along the airbag flap impossible.Because the tear forces in the transverse direction of the film laminate according to the invention are of the same order of magnitude as the tear forces in the longitudinal direction, and the tensile strengths are at the low level of 5 to 20 N / mm², it is surprisingly possible to achieve a contour-accurate opening of the airbag flap without having to weaken the laminate beforehand by creating weak points. This avoids, firstly, the visibility of the weakening line, which is considered a design flaw. Secondly, it saves the component manufacturer the costs associated with acquiring and operating machines for creating weakening lines.

[0010] According to an advantageous embodiment of the invention, the decorative layer is formed in two layers, consisting of an outer layer and an inner layer adjacent to the foam layer. This structure allows for better adaptation of the outer layer to the desired feel and appearance of the overall laminate, and the inner layer can be further optimized with regard to its tear resistance.

[0011] For good deep-drawing capability with the desired tensile strength and a pleasant feel, it has proven advantageous if the decorative layer has a thickness of 0.2 to 1 mm.

[0012] The outer layer of the film laminate can preferably have a thickness of 0.1 to 0.5 mm, and the inner layer adjacent to the foamed layer can also have a thickness of 0.1 to 0.5 mm.

[0013] The extruded decorative layer can be made up of one or more layers of plastic.

[0014] The plastic includes polyethylene (PE), polypropylene (PP) or mixtures of polyethylene (PE) and polypropylene (PP).

[0015] Polyethylene (PE) refers here to polymers or copolymers with an ethylene content exceeding 50% by weight. Polypropylene (PP) refers here to polymers or copolymers with a propylene content exceeding 50% by weight.

[0016] The plastic of the decorative layer may contain common additives such as lubricants, stabilizers, fillers (such as inorganic fillers), and / or pigments.

[0017] To achieve the most isotropic behavior possible with regard to tear forces, with a longitudinal to transverse direction ratio of 0.85 to 1.2, different approaches are possible.

[0018] Firstly, it is possible that the decorative layer, whether single- or multi-layered, contains polar and non-polar polymers within at least one layer. Due to the different polarities of the polymers, they do not mix homogeneously, and after extrusion of the film, the polar polymers lie like spheres in the non-polar matrix, thus weakening the tear resistance perpendicular to the extrusion direction. Polar polymers in combination with thermoplastic vulcanizates (TPVs), such as cross-linked EPDM, serve as an example of this.

[0019] On the other hand, isotropic tearing can be approximated by the targeted combination of high- and low-viscosity polymers with a viscosity / MFI difference of more than 6 g / 10 min according to DIN EN ISO 1133 within at least one layer of the decorative layer. In this case, the high-viscosity polymers lie like elongated islands within the matrix of low-viscosity polymers. An example of this is a combination of low-viscosity LDPE with high-viscosity PP. For PE, the MFI is measured according to DIN EN ISO 1133 at 190 °C / 2.16 kg, for PP at 230 °C / 2.16 kg, and for TPV at 230 °C / 10 kg.

[0020] A third possibility for approximating the tear forces in the longitudinal and transverse directions is to incorporate gas or air inclusions, preferably in the form of spherical hollow bodies, into the single- or multi-layered decorative layer within at least one layer. These hollow bodies act as disruptive elements to prevent tearing in the transverse direction. They could, for example, be hollow glass spheres.

[0021] The three aforementioned solutions can be used within a laminate, either in one or more layers, or in any combination. According to the invention, the second and / or the third solution is used.

[0022] For example, it is possible for spherical hollow bodies to consist of a layer made of a mixture of high- and low-viscosity polymers.

[0023] The foam layer of the film laminate can be based on the same plastics as the decorative layer layers, but it differs from the decorative layer in its foaming process and thus its density. Preferably, it is a polyolefin-based foam. The foam layer of the film laminate can be foamed either chemically by adding a solid, chemical blowing agent to the polymer composition, or physically. The polymer composition for the foam layer can contain other common components such as blowing agents, lubricants, stabilizers, fillers (such as inorganic fillers), and / or pigments.

[0024] The foam layer of the film laminate preferably has a thickness of 0.5 to 4 mm and a density of 40 to 200 kg / m³. Such a film laminate can be deep-drawn without any defects in the foam layer.

[0025] The film laminate according to the invention has a lacquer layer on its smooth or three-dimensionally structured surface of the decorative layer. The lacquer layer can be advantageous for improving surface properties, such as appearance or scratch resistance. The lacquer layer can be applied to the surface using conventional methods. The lacquer layer is preferably a polyurethane lacquer layer.

[0026] The film laminate is manufactured using conventional methods, whereby the decorative layer is extruded and coated with a lacquer layer. The foamed layer is preferably formed by foam extrusion, which can be achieved physically (with water or inert gases) or using chemical blowing agents. The layers are then bonded, for example, thermally or by adhesive bonding, to form a sheet material, resulting in a film laminate with a decorative layer and a foam layer. It is also possible to apply the lacquer layer after the other two layers have been bonded.

[0027] These flat laminates are further processed into components.

[0028] Various processes for forming components with three-dimensionally structured surfaces are known in the art. One example is the "in-mould graining" process (IMG process), which evolved as a specialized process from the negative deep drawing process. This in-mould graining process, previously known primarily by its English term, can perhaps best be translated as "negative deep drawing with grain." In contrast to the standard deep drawing process, in which the three-dimensional, component-geometric structure is formed by inserting a deep-drawing die into the sheet, forming the final component contour, in negative deep drawing a sheet is drawn into a negative mold, for example, by vacuum.The scar-forming negative deep drawing is a special form of negative deep drawing in which not only the component-geometric structure, but also the subsequent scar structure is introduced as a negative into the tool surface.

[0029] The film laminate according to the invention is particularly suitable for and geared towards the production of components using the IMG process or the positive thermoforming process.

[0030] The laminates produced for the positive thermoforming process can be subjected to a crosslinking step, preferably after the introduction of the three-dimensional surface structure, in particular electron beam crosslinking.

[0031] The laminate can be cross-linked using high-energy radiation, preferably electron beam radiation. This results in very good grain stability during positive thermoforming and excellent thermoforming properties. The irradiation causes cross-linking within the plastic.

[0032] The film laminate can be shaped according to a component, wherein the component shape is preferably obtained by applying the film laminate to a substrate that corresponds to the component shape using a shaping process step.

[0033] Preferably, the film laminate is used for coating components for the interior trim of motor vehicles, in particular at least in the area of ​​the airbag covers or in the area of ​​the tear seams of the airbag covers.

[0034] Surprisingly, the film laminate according to the invention can be used in the thermoforming process to produce an interior trim part for motor vehicles that exhibits tear behavior sufficient for airbag deployment, without requiring any subsequent weakening of the film laminate or component. The weakening lines, often perceived as flaws, can be omitted, thus eliminating the additional costs associated with introducing these lines (machinery, labor, working time).

[0035] The invention will now be explained in more detail using an exemplary embodiment, in which the only Figure 1The inventive film laminate 1 is shown schematically, comprising a two-layer decorative layer 2 with an outer layer 5 and an inner layer 6 adjacent to the foam layer 4. A lacquer layer 3 is applied to the outer layer 5 of the decorative layer 2. The lacquer layer 3 has a thickness of 7 µm. The outer layer 5 and the inner layer 6 each have a thickness of 0.4 mm, and the foam layer 4 is 2 mm thick. The film laminate 1 is provided with an embossed, three-dimensionally structured surface on the decorative layer 2, i.e., with a texture embossed on the outside by roller stamping.

[0036] This type of film laminate can be used for airbag covers in vehicle interior trim without the need for weakening lines. It can be processed using thermoforming.

[0037] Film laminates with the aforementioned layer structure were produced, with layer 6 of the decorative layer 2 being varied according to Tables 1, 2, and 3. The outer layer 5 was always a layer suitable for the positive thermoforming process and consisted of 33 wt% PP, 33 wt% ethyl propyl rubber, and 33 wt% EPDM (weight percent based on the polymers). The lacquer layer 3 was always a polyurethane lacquer, and the foam layer 4 was a polyolefin-based foam with a density of 67 kg / m³. The tear forces in the extrusion direction (longitudinal direction) and perpendicular to the extrusion direction (transverse direction) of the film laminates were determined according to DIN EN ISO 34 Method B Procedure b at 23 °C, and the tensile strengths according to DIN 527-3 Type 5 at 2000 mm / min at 23 °C in both the longitudinal and transverse directions. Laminates according to the invention are marked with E, comparable laminates with V.

[0038] The ingredients were as follows: TPV: PP / EPDM blend with 50 wt% EPDM, MFI 15 g / 10 min (230 °C / 10 kg), softening point approx. 165 °C. Polar polymer: Polylactic acid, density 1.2 g / cm³, melting point 145–160 °C, MFI 19 g / 10 min (230 °C / 2.16 kg). Compatibility enhancer 1: Acrylate-based terpolymer. Compatibility enhancer 2: High-viscosity LLD-PE (MFI 1 g / 10 min (190 °C / 2.16 kg)). High-viscosity LDPE: Low-density polyethylene, MFI = 1.9 g / 10 min at 190 °C / 2.16 kg. Low-viscosity PP: Propylene homopolymer, MFI = 10.0 g / 10 min at 230 °C / 2.16 kg, melt strength. 7 cN at a strain rate of 250 mm / s measured at a temperature of 200 °C: low-viscosity LDPE (low-density polyethylene), MFI = 9 g / 10 min at 190 °C / 2.16 kg; high-viscosity PP (propylene homopolymer), MFI = 1.0 g / 10 min at 230 °C / 2.16 kg; glass hollow spheres, diameter 35 µm

[0039] The melt flow index (MFI), as used here, is determined according to DIN EN ISO 1133 at a temperature of 230 °C for PP and 190 °C for PE, and a load of 2.16 kg. The melt flow index (MFI) is also referred to as the melt mass flow rate (MFR). Table 1 Components Unit 1(V) 2(V) 3(E) 4(E) TPV Weight parts 90 90 80 70 Polar polymer Weight parts 10 10 20 30 Compatibility mediator Weight parts - 5 5 5 Characteristics Tear force longitudinal N 8 10 11 12 Tear force transverse N 11 12 11 13 Ratio of longitudinal / transverse tear forces 0,7 0,8 1 0,9 Tensile strength longitudinal N / mm²< 15 12 7 5 Tensile strength transverse N / mm²< 18 15 8 5

[0040] According to Table 1, two immiscible polymers were used in the inner layer 6 of the decorative layer to achieve similar tear forces in the longitudinal and transverse directions. Airbag tests performed with the film laminates 3(E) and 4(E) yielded good results even without weakening lines. Table 2 Components Unit 5(V) 6(E) 7(V) 8(V) 9(E) 10(V) low viscosity LDPE Weight parts 40 70 80 - - - high viscosity PP Weight parts 40 10 10 - - - high viscosity LDPE Weight parts - - - 40 70 80 low viscosity PP Weight parts - - - 40 10 10 Compatibility assessment 2 Weight parts 20 20 10 20 20 10 Characteristics Tear force longitudinal N 25 14 16 30 19 28 Tear force transverse N 62 15 33 70 20 30 Ratio of longitudinal / transverse tear forces 0,4 0,9 0,5 0,4 0,9 0,9 Tensile strength longitudinal N / mm²< 15 13,5 27 29 13 24 Tensile strength transverse N / mm²< 18 15 32 33 14 27

[0041] According to Table 2, high- and low-viscosity polymers were used side by side in the inner layer 6 of the decorative layer to achieve similar tear forces in the longitudinal and transverse directions. Airbag tests carried out with the film laminates 6(E) and 9(E) yielded good results even without weakening lines. Table 3 Components Unit 11(E) high viscosity LDPE Weight parts 97,5 Glass hollow spheres Weight parts 2,5 Characteristics Tear force longitudinal N 26 Tear force transverse N 27 Ratio of longitudinal / transverse tear forces 0,9 Tensile strength longitudinal N / mm²< 9,2 Tensile strength transverse N / mm²< 11

[0042] According to Table 3, to achieve similar tear forces in the longitudinal and transverse directions, hollow glass spheres with a diameter of 35 µm were mixed into the polymer of the inner layer 6. Airbag tests carried out with the film laminate 11(E) yielded good results even without weakening lines.

Claims

1. Film laminate (1), comprising at least one or more layers, extruded decorative layer (2) with a varnish layer (3) on the upper side and a foam layer (4) on the underside, wherein the decorative layer is formed in one or more layers of plastic layers, wherein the plastic comprises polyethylene (PE), polypropylene (PP) or mixtures of polyethylene (PE) and polypropylene (PP), characterized in that the film laminate (1) has a tensile strength in accordance with DIN 527-3 Type 5 at 2000 mm / min at 23 °C from 5 to 20 N / rnm2 in the extrusion direction and perpendicular to the extrusion direction and the ratio of the tearing force of the film laminate (1) in the extrusion direction to the tearing force of the film laminate (1) perpendicular to the extrusion direction is 0.85 to 1.2, whereby the tearing force is determined in accordance with DIN EN ISO 34 Method B Method b at 23 °C, and wherein the ratio of the tearing force of the film laminate (1) in the extrusion direction to the tearing force of the film laminate (1) perpendicular to the extrusion direction of 0.85 to 1.2 is achieved by the fact that the single- or multi-layer decorative layer (2) contains polymers with a viscosity difference / MFI difference of more than 6 g / 10 min within at least one layer and / or the single- or multi-layer decorative layer (2) contains spherical polymers within at least one layer. The MFI is measured in accordance with DIN EN ISO 1133 for PE at 190 °C / 2.16 kg and for PP at 230 °C / 2.16 kg.

2. A film laminate (1) according to claim 1, characterized in that the decorative layer (2) is formed in two layers consisting of an outer layer (5) and an inner layer (6) adjacent to the foam layer (4).

3. A film laminate (1) according to claim 1 or 2, characterized in that the decorative layer (2) has a thickness of 0.2 to 1 mm.

4. A film laminate (1) according to claim 2 or 3, characterized in that the outer layer (5) has a thickness of 0.1 to 0.5 mm.

5. Film laminate (1) according to at least one of claims 2 to 4, characterized in that the inner layer (6) adjacent to the foamed layer has a thickness of 0.1 to 0.5 mm.

6. A film laminate (1) according to at least one of the preceding claims, characterized in that the foam layer (4) has a thickness of 0.5 to 4 mm and a density of 40 to 200 kg / m3.

7. An interior trim part for motor vehicles, preferably a dashboard, which is provided with a film laminate (1) according to one of claims 1 to 6 at least in the area of the airbag covers or in the area of the tear seams of the airbag covers.