MULTILAYER STRUCTURE FOR AUTOMOTIVE COMPONENTS

Abstract

The invention relates to a multilayer structure comprising: two outer layers a1, made of a non-woven material; at least one intermediate layer ß, made of a glass wool material; at least one intermediate polyurethane layer ?; wherein the at least one intermediate polyurethane layer ? is made of polyurethane derived from automotive polyurethane waste and wherein the at least one intermediate polyurethane layer ? has a density value in the range of 20 to 30 g / l.

Description

MULTILAYER STRUCTURE FOR AUTOMOTIVE COMPONENTS Field of Invention The present invention relates to a multilayer structure that achieves desired acoustic absorption, thermal insulation, structural rigidity and lightness performance, while at the same time being environmentally sustainable. This innovative multi-layer structure is suitable for preparing various automotive components located in different parts of the vehicle. The multi-layer structure is manufactured using automotive production waste, offcuts, and off-specification products, which consequently has a positive impact on the environmental footprint, as will be demonstrated below. Furthermore, it reduces the vehicle's weight, decreasing energy consumption while maintaining valid structural and mechanical properties. Background of the Invention Currently, the automotive industry faces several problems related to the needs arising from both environmental protection and the well-being and comfort of passengers and citizens: reduction of vehicle mass, significant decrease in emissions, better use of resources employed, that is, focusing on reducing byproducts or production waste, reduction of outputs, Ref. 331278 off-specification products, etc. This will become increasingly true in the coming years, when at least 25% of internal combustion engines will be replaced by electric motors, thus making the need for mass reduction even more critical. This need stems from the necessity to reduce weight in order to gain mass and space for electric batteries and reduce energy consumption. In addition to this, drivers and passengers are already demanding quieter interiors, while reducing exterior car noise will be mandatory, at least in Europe, according to EEC Regulation No. 540 / 2014. To dampen engine noise and prevent heat and energy dissipation in the engine compartment, car suppliers are required to provide shielding or specific panels / components placed in different locations on the vehicle to overcome insulation problems. Such components are normally made of inorganic compounds bonded with thermosetting or thermosetting resins, generally combined with layers of different area / weight of organic material with glass fibers / fillers (SMC) or even rubber (filled with inorganic materials). Alternatively, engine cowls are available. These are manufactured from inorganic composites combined with natural fibers, reinforced with injection-molded parts of thermosetting polymers. These polymers are treated for oil / fluid / fire resistance before assembly. The materials used for the structural layer are usually natural fibers, sometimes bonded with thermosetting powders or thermoplastic fibers; polyurethane foams are sometimes applied for the same purpose. Additional coatings with aesthetic / functional surface materials, along with adhesive layers, are necessary, primarily for thermal insulation. Currently, such thick multi-layered structures not only have the problem that their thickness decreases, which is necessary to ensure flexural rigidity, drastically reducing acoustic absorption, but they also suffer from so-called sandwich fragility. This phenomenon is also related to the use of lightweight polyurethane foams, which can decrease the weight of the overall structure, but cause a constant problem in the automotive industry, as it is a source of structural weakness. In fact, the technology known for this type of automotive component meets acoustic and thermal performance requirements, but to ensure structural properties and stability performance, such components turned out to be very heavy, inflexible, with limited integration capacity and reduced structural properties. In fact, a typical weight value of the present protective or armor components (with respect to the surface), obtained via injection molding, is between 3.0 and 4.0 Kg / m2 and the density of the material is between 1400-1500 Kg / m3. Therefore, there is a perceived need to provide lighter structures and reduce vehicle mass without compromising material performance. This requirement is particularly advantageous in electric vehicles, where the demand for weight reduction can offer additional opportunities to increase range, allowing the weight saved to be used for more batteries. Therefore, automotive suppliers are required to find an intermediate solution and develop lighter, structurally strong, and flexible structures to meet these challenging demands. Along with the above objectives, it is necessary to find sustainable solutions, capable of combining an environmentally friendly material with high-performance structures. Therefore, the main objective of the present invention is to provide automotive components made of high-performance lightweight structures, as well as to recycle automotive waste materials, avoiding their dumping or incineration. Brief Description of the Invention Surprisingly, it has been found that polyurethane waste from automobiles can be used by assembling it together with other materials, avoiding the disposal of waste polyurethane components from automobiles. Such polyurethane waste can be used to manufacture a multi-layered structure to prepare other automotive components. Therefore, the present invention relates to a multilayer structure comprising: two outer layers, made of a non-woven material; at least one intermediate β layer, made of glass wool fiber; at least one intermediate layer of γ polyurethane; wherein at least one intermediate polyurethane layer γ is manufactured from polyurethane derived from automotive polyurethane waste and wherein at least one intermediate polyurethane layer γ has a density value in the range of 20 to 30 g / L. In a preferred embodiment, the multilayer structure according to the invention has the following sequence of layers: 1) an outer layer to; 2) at least one intermediate β layer; 3) at least one intermediate layer of γ polyurethane, with a density value in the range of 20 to 30 g / 1 and 4) an outer layer to the. In another preferred embodiment, the multilayer structure according to the invention has the following sequence of layers: 1) an outer layer to; 2) at least one intermediate layer of polyurethane γ having a density value in the range of 20 to 30 g / 1; 3) at least one intermediate β layer and 4) an outer layer to the. Advantageously, layers 2) and 3) of the preferred embodiments of the invention are repeated at least twice. The present invention also relates to a process for preparing the multilayer structure of the invention, the process comprising the following steps: a) provide automotive polyurethane waste having a density value in the range of 20 to 30 g / 1; b) cutting a glass wool fiber into sheets having a two-dimensional shape suitable for a molding step f), thereby obtaining at least one β-layer sheet made of glass wool fiber; c) cutting the automotive polyurethane waste from step a) into sheets having a two-dimensional shape suitable for a molding step f), thus obtaining at least one γ-layer sheet, made from polyurethane waste having a density value in the range of 20 to 30 g / liter; d) cutting a non-woven material into sheets having a two-dimensional shape of twice the two-dimensional shape of the β layer of the γ layer, thus obtaining at least one non-woven sheet; e) fold at least one non-woven sheet from step d), thus obtaining two outer layers to; f) insert the β and Y layers, from steps b) and e), respectively, between the two outer layers of e), thus obtaining a sandwich set; g) load the sandwich assembly into a heat molding device; h) mold the sandwich assembly above via thermocompression, at a temperature in the range of 190 to 200°C; i) obtain the multilayer structure of the invention. Advantageously, the insertion step f) allows obtaining different sandwich sets to prepare different multilayer structures, as will be evident from the figures and examples presented below. As will become more evident below in the experimental part, the multilayer structure of the invention achieves the desired acoustic absorption, structural and mechanical performances, while being lighter and more sustainable, compared to known structures for automotive purposes. Advantageously, the multilayer structure of the invention therefore has a balanced integration of functions, namely thermal, acoustic, and mechanical functions. The properties of the multilayer structure are also enabled by the sandwich-like assembly of its materials, which simultaneously achieves the objective of being lighter than known structures, avoiding the sandwich-like fragility problem of known structures, and increasing overall resilience, flexibility, and strength. In a first preferred embodiment, the multilayer structure comprises at least one intermediate β layer and at least one intermediate γ layer repeated alternately at least 2 times. Without being limited by any theory, and as will be evident from the detailed description and examples, the characteristics of the multilayer structure and the combination of materials used allow us to obtain a final automotive article that has a good compromise between lightness, mechanical and structural properties, weight, and sustainability. Therefore, the present invention provides an automotive component manufactured from the multi-layer structure of the invention. Such an automotive component encompasses optimal technical characteristics along with the possibility of reducing secondary products and discarded production materials, as well as recycling automotive waste materials. It is evident that the multi-layer structure obtained through the recovery process of automotive polyurethane waste, which has a density value in the range of 20 to 30 g / 1, and the automotive component manufactured from it, allows car manufacturers to achieve the compromise of having at the same time a resistant, rigid material and a lightweight and flexible product, while ensuring acoustic and thermal performance. Brief Description of the Figures Figure 1 shows a multilayer structure of the invention, as prepared in Examples 1-4; Figure 2 shows an alternative multilayer structure of the invention, as prepared in Examples 9, 10; Figure 3 shows a comparison of acoustic tests of the samples of the invention, as prepared in Examples 9 and 10 without an air gap; Figure 4 shows a comparison of acoustic tests of the samples of the invention, as prepared in Examples 9 and 10 with an air gap of 10 mm; Did I laugh? Lnn / zznz / E / YiAi Figure 5 shows a stone impact test image of the multilayer structure of the invention, prepared in accordance with Example 9 and Figure 6 shows a stone impact test image of the multi-layer structure of the invention, prepared according to Example 10. Detailed Description of the Invention Therefore, the present invention relates to a multilayer structure comprising: two outer layers, made of a non-woven material; at least one intermediate β layer, made of glass wool fiber; at least one intermediate layer of γ polyurethane; wherein the at least one intermediate polyurethane γ layer is manufactured from polyurethane derived from automotive polyurethane waste and wherein the at least one intermediate polyurethane γ layer has a density value in the range of 20 to 30 g / 1. In the present invention, the following terms apply: Automotive waste or scrap means any scrap or waste, waste, discarded polyurethane materials derived from automotive polyurethane parts and having a density value in the range of 20 to 30 g / 1; Did I laugh? Lnn / zznz / E / YiAi external means any external layer, which acts as upper and lower layers, employed in the multilayer structure; intermediate refers to any internal layer, placed between the external layers, present in the multilayer structure. The multi-layer structure comprises at least one intermediate layer of γ polyurethane derived from automotive scrap and having a density value in the range of 20 to 30 g / 1, thus combining lightness, remarkable mechanical and structural properties, as will be clear from the detailed description and examples, and enabling sustainable recycling of polyurethane waste. Surprisingly, these characteristics have been achieved by using polyurethane waste directly to prepare the multilayer structures of the invention without being treated or subjected to any type of chemical treatment before assembling them into the final structure. In a first preferred embodiment, the multilayer structure comprises at least one intermediate layer β made of glass wool fiber and / or at least one intermediate layer γ, wherein the at least one intermediate layer β and / or at least one intermediate layer γ are repeated, independently of each other, at least twice. In a second preferred embodiment, the multilayer structure comprises at least one intermediate layer γ with at least one intermediate layer β made of glass wool fiber between them. In a preferred embodiment, the multilayer structure according to the invention has the following sequence of layers: 1) an outer layer, made of a non-woven material; 2) at least one intermediate layer β, of glass wool fiber; 3) at least one intermediate layer of γ polyurethane, manufactured from automotive polyurethane scrap with a density value in the range of 20 to 30 g / 1 and 4) an outer layer, made of a non-woven material. In another preferred embodiment, the multilayer structure according to the invention has the following sequence of layers: 1) an outer layer, made of a non-woven material; 2) at least one intermediate layer of polyurethane γ having a density value in the range of 20 to 30 g / 1; 3) at least one intermediate layer β, made of glass wool fiber and 4) an outer layer, made of a non-woven material. Advantageously, layers 2) and 3) of the preferred embodiments of the invention are repeated at least twice. Did I laugh? Lnn / zznz / E / YiAi According to the invention, the intermediate layer γ is manufactured from polyurethane derived from automotive polyurethane waste. This polyurethane of the γ layer is a lightweight material, having a density value in the range of 20 to 30 g / L, preferably 22 to 25 g / L. The density value of polyurethane waste can be measured according to well-known measurements in the art, for example, ISO 845. More preferably the polyurethane of the γ layer has a density of 25 g / 1, even more preferably 22 g / 1. The at least one intermediate polyurethane γ layer preferably has an elongation at break value in both directions in a range of 40 to 150% (according to EN ISO 9073-3). The at least one intermediate polyurethane layer γ preferably has a permanent compression deformation of 1000-1200 g / cm2 (according to DIN EN ISO 1856). Advantageously, in addition to these properties, the at least one intermediate layer of γ polyurethane also exhibits sound-absorbing and self-extinguishing characteristics, and is non-combustible. The flammability value of the γ layer is surprisingly 100 mm / minute. The γ layer preferably has a tear strength in both directions of 14 N / cm2 (according to EN ISO 1798) and an elongation value in both directions of 40%. The multilayer structure comprises two external layers, one placed as the top layer and the other as the bottom layer. The material of the two outer layers, made of non-woven material, could be selected based on the end use of the automotive component manufactured with the multi-layer structure of the invention. Through different combinations, it is possible to change the area of ​​the vehicle where the component can be placed, thus ensuring flexible application of the novel material solution. In a first embodiment, the nonwoven material of the outer layer is preferably made of viscose and polyester, more preferably with a total weight of 100-120 g / m² according to EN ISO 9073-1. Advantageously, and even more preferably, the nonwoven material is made of viscose / polyester-PET based fibers, coated with a phenolic coating. The two outer layers made of viscose-polyester-PET based fibers are preferably thin layers that have, more preferably: a thickness at 1 KPa of approximately 0.78 mm, according to EN ISO 9073-2. a maximum tensile strength at break in the machine direction, at a speed of 100 mm / minute (according to EN ISO 9073-3) of approximately 86.7 N / 5 cm, a maximum tensile strength at break in the transverse direction of approximately 122.1 N / 5 cm; The two outer layers, made of viscose-polyester-PET fibers, have good flexibility, an elongation at maximum breaking strength in the machine direction at a speed of 100 mm / min, according to EN ISO 9073-3, of approximately 46.7%, and an elongation at maximum breaking strength in the transverse direction at a speed of 100 mm / min, according to EN ISO 9073-3, of approximately 77.6%. They also advantageously possess oil / water / diesel repellency and have a flammability value of approximately 0. In another embodiment, the outer layers are preferably made of a carbon nonwoven material, more preferably a needle-punched carbon nonwoven material, even more preferably made of a polyester fiber cloth (pre-oxidized polyacrylonitrile C fibers), coated with a phenolic coating. The outer layer made of a carbon non-woven material preferably has a total surface weight in the range of 100 to 120 g / m2, in accordance with EN ISO 9073-1. The two outer layers comprising a carbon nonwoven material are preferably thin layers that have, preferably: a thickness at 1 kPa of approximately 1 mm, according to EN ISO 9073-2; a maximum tensile strength at break in the machine direction, at a speed of 100 mm / minute, in accordance with EN ISO 9073-3, of at least 30 N / 5 cm and a maximum tensile strength at break in the transverse direction of at least 40 N / 5 cm The two outer layers comprising a carbon non-woven material preferably have good flexibility, have elongation at maximum breaking strength, in the machine direction, at a speed of 100 mm / min, according to EN ISO 9073-3, of at least 30% and an elongation at maximum breaking strength in the transverse direction, at a speed of 100 mm / min, according to EN ISO 9073-3, of at least 60%. They also possess oil / water / diesel repellency, which has a flammability value of approximately 0. The multi-layer structure comprises at least one intermediate layer β, made of fiberglass. This layer provides good thermal and acoustic insulation performance for the vehicle's engine compartment. In the β layer of the invention, the glass wool fiber is preferably bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% relative to the total weight of the β layer, with very low formaldehyde emissions. The intermediate β layer may further comprise a flame retardant additive. The at least intermediate layer β containing the flame retardant additive preferably has a compressive load flexure in the range of 3 to 5 kPa at 40% deformation (according to DIN EN ISO 3386 / 1), a permanent deformation of a maximum of 8% at 50% deformation (according to DIN EN ISO 1856), an elongation at break of at least 150% (according to DIN EN ISO 1798) and a tensile strength of at least 150 kPa (according to DIN EN ISO 1798). In a preferred and advantageous embodiment of the invention, the multilayer structure comprises: two outer layers, made of a non-woven material consisting of a 50 / 50 viscose-polyester-PET based fiber blend covered with a phenolic coating, having a total surface weight in the range of 100 to 120 g / m2 with respect to a multilayer structure sample of 100 cm2 and a thickness of 0.78 mm. at least one intermediate layer of β glass wool, made from a glass wool fiber bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% relative to the total weight of the β layer, with very low formaldehyde emission and a flame retardant additive. at least one intermediate layer of γ polyurethane having a density value of 25 g / 1. In another preferred and advantageous embodiment of the present invention, the multilayer structure comprises: two outer non-woven carbon al layers, made of a polyester fiber C-fabric (pre-oxidized polyacrylonitrile C fibers) covered with a phenolic coating, having a total surface weight in the range of 100 to 120 g / m2 with respect to a multi-layer structure sample of 100 cm2 and a thickness at 1 KPa of 1 mm. at least one intermediate layer of β glass wool, made from a glass wool fiber bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% with respect to the total weight of the β layer, with very low formaldehyde emission and comprising a flame retardant additive (fireproof or fire retardant). at least one intermediate layer of γ polyurethane having a density value of 25 g / 1. In another preferred and advantageous embodiment of the invention, the multilayer structure comprises: two outer layers, made of a non-woven material consisting of a 50 / 50 viscose-polyester-PET based fiber blend covered with a phenolic coating, having a total surface weight in the range of 100 to 120 g / m2 with respect to a multilayer structure sample of 100 cm2 and a thickness of 0.78 mm. at least one intermediate layer of β glass wool, made from a glass wool fiber bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% with respect to the total weight of the β layer, with very low formaldehyde emission and comprising a flame retardant additive. at least one intermediate layer of γ polyurethane having a density value of 22 g / 1. In another preferred and advantageous embodiment of the present invention, the multilayer structure comprises: two outer non-woven carbon al layers, made of a polyester fiber C-fabric (pre-oxidized polyacrylonitrile C fibers) covered with a phenolic coating, having a total surface weight in the range of 100 to 120 g / m2 with respect to a multi-layer structure sample of 100 cm2 and a thickness at 1 kPa of 1 mm. at least one intermediate layer of β glass wool, made from a glass wool fiber bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% with respect to the total weight of the β layer, with very low formaldehyde emission and comprising a flame retardant additive. at least one intermediate layer of γ polyurethane having a density value of 22 g / 1. As indicated above, the β and γ layers, or each considered individually, are repeated independently of each other at least twice, as will be clearer from the experimental part. For example, the following structure can be cited: Three β layers can be stacked to obtain a multilayer structure, between the two intermediate γ layers and within the two outer layers, and two repetitions of β and γ layers can be stacked to obtain a multilayer structure, between the two outer layers. The multilayer structures of the invention showed very good performance, preferably showing: Flexural moduli (E): from 380 to 1600 N / mm2, preferably 550-950 N / mm2 measured in accordance with ISO 179 via the 3-point bending method (Charpy method), using 10 rectangular samples of the multi-layer structure (50 x 160 mm), through a 10 mm diameter punch at a loading rate of 10 mm / minute, with a distance between supports of 100 mm and with a press pressure of 150 bar. Breaking load: 40 to 80 N, measured according to ISO 179, via the 3-point bending method (Charpy method), described above. Flexural strength: 7 to 15 N / mm2, measured via the 3-point bending method described above. density (Kg / m3): from 500 to 1000 Kg / m3 using 3 samples (100 x 100 mm) taken from different parts of the examined sample of the multilayer structure and determine the mass / volume ratio using the approximate values ​​of 0.1 mm for the thickness of the samples, 0.5 mm for the sides of the samples and 0.1 g for the mass of the samples. tensile strength: from 4 to 16 N / mm2 according to ISO 179, using 10 rectangular samples of the multilayer structure according to the invention (50 x 160 mm) and tensile testing of the samples with a feed rate of 100 mm / minute until breakage. Therefore, in another aspect, the invention relates to an automotive component manufactured from the multilayer structure of the invention. Possible automotive components include: wheel arches, retractable hardtops with air ducts, trunk floor covers, and underbody panels. All of these automotive components can be fitted to different vehicles and in different locations within the vehicle. In another aspect, the invention therefore relates to a process for preparing the multilayer structure of the invention, the process comprising the following steps: a) provide automotive polyurethane waste having a density value in the range of 20 to 30 g / 1; b) cutting a glass wool fiber into sheets that have a two-dimensional shape suitable for a molding step f), thus obtaining at least one β-layer sheet, made of glass wool fiber; c) cutting the automotive polyurethane waste from step a) into sheets having a two-dimensional shape suitable for molding step f), thereby obtaining at least one γ-layer sheet, made from polyurethane waste, having a density value in the range of 20 to 30 g / 1; d) cutting a non-woven material into sheets that have a two-dimensional shape twice the two-dimensional shape of the β layer or γ layer, thus obtaining at least one non-woven sheet; e) fold at least one non-woven sheet from step d), thus obtaining two outer layers to; f) insert the β and Y layers, from steps b) and e), respectively, between the two outer layers of e), thus obtaining a sandwich set; g) load the sandwich assembly into a heat molding device; h) mold the sandwich assembly above via thermocompression, at a temperature in the range of 190 to 200°C; i) obtain the multilayer structure of the invention. Preferably, the cutting, of steps b), c) and d) is carried out with at least one blade that has a force of 25 Kg / mm. Did I laugh? Lnn / zznz / E / YiAi The insertion step f) provides the insertion of layers β and γ, from steps b) and i) into a desired sandwich assembly having a sequence of layers as indicated above in the preferred embodiments of the invention. The invention will be further detailed in the following experimental part, reporting examples and tests or trials on the multilayer structure, comprising at least one intermediate layer γ made of polyurethane derived from automotive polyurethane waste. Experimental Part Example 1 Preparation of a multilayer structure 1, as shown in Figure 1 The multilayer structure 1 in Figure 1 was prepared using a steel thermoforming tool mounted on a vertical press. With reference to Figure 1, the following multilayer structure was prepared: two outer layers, made of non-woven viscose-polyester layers comprising polyester, having a total surface weight in the range of 100 to 120 g / m2 with respect to a 100 cm2 multilayer structure sample, a thickness of 0.78 mm and made of a 50 / 50 blend of viscose / polyester-black PET fibers, covered with a phenolic coating. Did I laugh? Lnn / zznz / E / YiAi three intermediate layers of β glass wool, made from a glass wool fiber bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% with respect to the total weight of the β layer, with very low formaldehyde emission and flame retardant additive. two intermediate layers of γ polyurethane that have a density value of 25 g / 1. First, automotive polyurethane waste was provided. Glass wool fiber was cut into rectangular sheets suitable for fitting into the molding device, yielding three β-layer sheets made of glass wool fiber. Next, automotive polyurethane waste was cut into sheets with the same rectangular shape as the glass wool fiber sheet, yielding two γ-layer sheets. The polyurethane sheet had a permanent compression set in the range of 1000 to 1200 g / cm³, a bidirectional tear strength of 14 N / cm², and a bidirectional elongation value of 40–150%. A nonwoven material was cut into sheets twice the size of the rectangular β-layer, yielding a nonwoven sheet. This sheet was then folded to create two outer layers. The three β layers and the two γ layers were inserted alternately according to the layer sequence reported in Figure 1. The final sandwich assembly was loaded into the heat molding device and molded via thermocompression at a temperature of 190-200°C for a time equal to or less than 60 seconds, thus obtaining the multilayer structure of the invention shown in Figure 1. Example 2 Preparation of a multilayer structure 2 as shown in Figure 1 By following the same procedure as in Example 1, using the layers indicated below, the multilayer structure 2 has been prepared. With reference to Figure 1, the following layers were used: two outer non-woven carbon al layers, made of PAÑO fibers (pre-oxidized polyacrylonitrile C fibers) polyester covered with a phenolic coating, having a total surface weight in the range of 100 to 120 g / m2 with respect to a sample of multilayer structure of 100 cm2 and a thickness at 1 Kpa of 1 mm. three intermediate layers of β glass wool, made from a glass wool fiber bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% with respect to the total weight of the β layer, with very low formaldehyde emission and comprising a flame retardant additive. two intermediate layers of polyurethane γ that have a reí value? Lnn / zznz / E / YiAi of density of 25 g / 1. The polyurethane layer γ had a permanent compression set in the range of 1000 to 1200 g / cm³, a tear strength in both directions of 14 N / cm², and an elongation value in both directions of between 40 and 150%. Example 3 Preparation of a multilayer structure 3, as shown in Figure 1 By following the same procedure as in Example 1, using the layers indicated below, the multilayer structure 3 has been prepared. With reference to Figure 1, the following layers were used: two outer layers, made of needle-punched nonwoven layers comprising viscose-polyester, having a total surface weight in the range of 100 to 120 g / m2 with respect to a 100 cm2 multilayer structure sample, a thickness of 0.78 mm and made of a 50 / 50 blend of black viscose / polyester-PET fibers, covered with a phenolic coating. three intermediate layers of β glass wool, made from a glass wool fiber bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% relative to the total weight of the β layer, with very low formaldehyde emission and comprising a flame retardant additive. Did I laugh? Lnn / zznz / E / YiAi two intermediate layers of γ polyurethane that have a density value of 22 g / 1. The polyurethane layer γ had a permanent compression set in the range of 1000 to 1200 g / cm³, a tear strength in both directions of 14 N / cm², and an elongation value in both directions of between 40 and 150%. Example 4 Preparation of a multilayer structure 4, as shown in Figure 1 By following the same procedure as in Example 1 using the layers indicated below, the multilayer structure 4 has been prepared. With reference to Figure 1, the following layers were used: two outer non-woven carbon al layers, made of PAÑO fibers (pre-oxidized polyacrylonitrile C fibers) polyester covered with a phenolic coating, having a total surface weight in the range of 100 to 120 g / m2 with respect to a multilayer structure sample of 100cm2 and a thickness at 1 kPa of 1 mm. three intermediate layers of β glass wool, made from a glass wool fiber bonded with thermosetting phenolic resin binder (R225) in an amount of 10% with respect to the total weight of the β layer, with very low formaldehyde emission and comprising a flame retardant additive. Did I laugh? Lnn / zznz / E / YiAi two intermediate layers of γ polyurethane that have a density value of 22 g / 1. The polyurethane layer γ had a permanent compression set in the range of 1000 to 1200 g / cm³, a tear strength in both directions of 14 N / cm², and an elongation value in both directions of between 40 and 150%. Example 5 Comparison of the density and weight of the multilayer structure of the invention with respect to a prior art material. In the automotive field, a prior art material used in the production of automotive components, such as wheel arches, retractable hardtops with air ducts, trunk floor covers, and underbody covers, is polyamide reinforced with 30% glass fibers (FCA STANDARD MS.50017). Such a material is commercially available as PA GF30 (i.e., Durethan BKV 30H produced by Bayer, Zytel 73G30 produced by Dupont, and TECHNYL C218 V30 produced by NYLTECH) and is obtained using the well-known injection molding technology. A sample of the previously known material was compared with the multilayer structure of the invention. Specifically, in the comparison test, the multilayer structure of the invention was used according to Example 1, as depicted in Figure 1. The prior art material (PA GF30) and the multilayer reí? Lnn / zznz / E / YiAi structure of the invention were tested to evaluate density and weight. The material from the previous technique turned out to have a density of 1400 Kg / m2 and a weight of 3.0 Kg. The multi-layer structure of the invention resulted in a density of 543 Kg / m2 and a weight of 1.2 Kg. From the results reported above, the weight reduction obtained with the multilayer structure of the invention was approximately 61.2% compared to the material known in the prior art. It is evident that the multilayer structure of the invention allows for the preparation of lighter automotive components, thus reducing their weight and the final mass of the vehicle. Example 6: Comparison of different automotive components, manufactured from the multilayer structure of the invention, with respect to automotive components, manufactured from the material known in the prior art. The automotive components, namely wheel arches, retractable hardtops with air ducts, trunk floor covers, and underbody covers, were prepared using the same material as in the prior art of Example 5. The resulting samples were used as comparative samples. The multilayer structure of Example 1 was used to prepare the same automotive components, namely wheel arches, retractable hardtops with air ducts, trunk floor covers, and underbody covers. The following properties of automotive components, manufactured from prior art material and automotive components, manufactured from the multilayer structure of the invention, were evaluated: lightness, sound insulation, sound absorption, aesthetic property, mechanical property, structural property, stone impact resistance, resilience and flame resistance. The evaluation consisted of assigning a score on a scale of --- to +++ with respect to the reference. The results are reported in Table 1. Table 1 laughed? Lnn / zznz / E / YiAi Property Automotive Components Wheel Arch Air Ducts Retractable Hood Trunk Floor Cover Lower Body Side Covers Lightness +++ +++ +++ +++ +++ Sound Insulation +++ +++ +++ +++ +++ Sound Absorption ++ ndndnd ++ Aesthetic Properties ++ nd ++ ++ ++ Mechanical Properties ++ nd ++ ++ ++ Structural Properties ++ ++ ++ ++ ++ Stone Impact Resistance +++ ndndnd +++ Elasticity (Brittleness) +++ +++ +++ +++ +++ Flame Resistance, STD (FMVSS 302) +++ +++ +++ +++ +++ Flame Resistance (UL94) +++ +++ ndndndnd not determined Automotive components, manufactured from the multilayer structure of the invention, showed better properties compared to automotive components manufactured from the material of the prior art. Specifically, they were surprisingly lighter, more resistant to stone impact, and exhibited better resilience or elasticity and flame resistance compared to comparative samples. Furthermore, the samples of the invention showed improved sound absorption and better aesthetic, mechanical, and structural properties. Example 7: Evaluation of the flexural modulus (E) of the multilayer structures of the invention Multilayer structure 1, prepared according to example 1, and multilayer structure 3, prepared according to example 3, were evaluated by measuring the bending modulus E via the 3-point bending method (Charpy method, according to ISO 179 - flat sheets). Specifically, ten rectangular samples (50 x 160 x 3 mm thick) of multilayer structures 1 and 3 were provided, respectively. All samples of the invention were tested through a 10 mm diameter punch with a loading speed of 10 mm / minute, with a distance between supports 16 times the thickness of the multi-layer structure (100 mm) and with a press pressure of 150 bar. Did I laugh? Lnn / zznz / E / YiAi The Flexural Modulus (E) was evaluated according to formula (I): P l3 Hey F b * s3en where P is the load (N) b is the width of the test tube (mm) is the distance between supports (mm) s is the thickness of the test tubes (mm) P / F is the slope of the initial straight section of the deformation load curve. The results for the samples of the multilayer structure 1 of the invention and of the multilayer structure 3 are reported in the following tables 2 and 3, respectively. Did I laugh? Lnn / zznz / E / YiAi Table 2 Samples 1 2 3 4 5 6 7 8 9 10 Maximum load (N) 64.0 75.5 61.5 54.0 76.0 78.0 74.5 49.0 60.5 42.5 Flexural modulus (E) 462.9 259.5 548.7 457.9 383.6 510.0 528.2 472.6 334.0 468.5 Table 3 Samples 1 2 3 4 5 6 7 8 9 10 Maximum load (N) 71.0 60.0 73.0 63.5 53.0 54.0 60.5 56.0 48.5 56.0 Flexural modulus (E) 1480.9 1201.3 1458.5 1519.5 1380.6 1503.9 1166.8 1570.7 1290.1 ​​1583.0 The average values ​​of the flexural modulus have been calculated for both multilayer structures of the invention and the following results have been obtained: Maximum load Flexural modulus Multilayer structure 1 63.6 442.6 Multilayer structure 3 59.6 1415.5 Both multilayer structures of the invention exhibited good flexibility properties. Multilayer structure 1, prepared according to Example 1, comprising at least one intermediate layer of γ-polyurethane with a density of 25 g / L, showed very good flexibility. Multilayer structure 3, prepared according to Example 3, comprising at least one intermediate layer of γ-polyurethane with a density of 22 g / L, showed an increase in Flexibility Modulus of approximately 31% compared to multilayer structure 1. Multilayer structure 3, therefore, proved to be the preferred one for the evaluated property and stress management. Example 8: Evaluation of tensile strength of multilayer structures of the invention The same samples used in example 7 were also evaluated for tensile strength according to ISO 179. Specifically, ten rectangular samples (50 x 160 x 3 mm thick) of multilayer structures 1 and 3, respectively, were provided and stretched at a feed rate of 100 mm / minute, until they broke. The Tensile Strength (R) was evaluated according to formula (II): P*l H — — * ---- b * s2en where P is the load (N) b is the width of the test tube (mm) 1 is the distance between supports (mm) s is the thickness of the test tubes The results for the samples of the multilayer structures 1 and 3 are reported in tables 4 and 5, respectively. Did I laugh? Lnn / zznz / E / YiAi Table 4 Samples 1 2 3 4 5 6 7 8 9 10 Tensile strength 6.3 4.4 7.5 6.6 5.6 7.8 7.9 7.6 4.7 6.0 Table 5 Samples 1 2 3 4 5 6 7 8 9 10 Tensile strength 14.7 11.7 12.4 15.4 12.1 11.7 10.7 12.6 11.7 10.1 The average tensile strength values ​​for both multilayer structures 1 and 3 have been calculated and the following results have been obtained: Maximum load Tensile strength Multilayer structure 1 63.6 6.4 Multilayer structure 3 59.6 12.3 Both multilayer structures of the invention exhibited good tensile strength properties. Multilayer structure 1 showed good tensile strength. Multilayer structure 3, prepared according to Example 3, comprising at least one intermediate layer of polyurethane γ with a density value of 22 g / L, showed an increase in tensile strength of approximately 52% compared to the multilayer structure prepared according to Example 1, comprising at least one intermediate layer of polyurethane γ with a density value of 25 g / L. The multilayer structure 3 thus proved to be the preferred option due to its greater resistance under mechanical and structural stress. Example 9 Preparation of the multilayer structure 5 of the invention, as depicted in Figure 2 By following the same procedure as in Example 1 using the layers indicated below, the multilayer structure 5 has been prepared, which has a different sequence of layers. With reference to figure 2, the following layers were used: two outer layers, made of needle-punched nonwoven layers comprising viscose-polyester, having a total surface weight in the range of 100 to 120 g / m2 with respect to a 100 cm2 multilayer structure sample, a thickness of 0.78 mm and made from a 50 / 50 blend of black viscose / polyester-PET fibers, covered with a phenolic coating. two intermediate layers of γ polyurethane that have a density value of 25 g / 1. Three intermediate layers of β-glass wool, manufactured from glass wool fiber bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% relative to the total weight of the β layer, with very low formaldehyde emissions and comprising a flame retardant additive. Example 10 Preparation of the multilayer structure 6 of the invention, as shown in Figure 2 By following the same procedure as in example 1, using the layers indicated below, the multilayer structure 6 has been prepared. With reference to figure 2, the following layers were used: two outer non-woven carbon al layers, made of PAÑO fibers (pre-oxidized polyacrylonitrile C fibers) polyester covered with a phenolic coating, having a total surface weight in the range of 100 to 120 g / m2 with respect to a sample of multilayer structure of 100 cm2 and a thickness at 1 Kpa of 1 mm. three intermediate layers of β glass wool, made from a glass wool fiber bonded with a thermosetting phenolic resin (R225) binder in an amount of 10% with respect to the total weight of the β layer, with very low formaldehyde emission and comprising a flame retardant additive. two intermediate layers of γ polyurethane that have a density value of 25 g / 1. Example 11 Acoustic performance evaluation of the multilayer structures of the invention The acoustic performances of multilayer structure 5, prepared according to example 9, and multilayer structure 6, prepared according to example 10, were compared. Specifically, multilayer structure 5 had a weight of 3.43 g, a weight per area of ​​2157 g / m2, a thickness of 2.7 mm and a density of 811 Kg / m3, while multilayer structure 6 had a weight of 3.66 g, a weight per area of ​​2301 g / m2, a thickness of 3.0 mm and a density of 767 Kg / m3. Acoustic testing was performed using an ASTM 1050.95 impedance tube (Kundt tube) in accordance with ISO 10534-2, at 21°C and 49% humidity. The test was repeated twice with air gaps of 0 mm and 10 mm. The results are reported in Figures 3 and 4, respectively. In Figure 3 (air gap = 0 mm) and Figure 4 (air gap = 10 mm) the dashed line represents the multilayer structure 6 prepared according to example 10 and the solid black line represents the multilayer structure 5 prepared according to example 9. Multilayer structure 6 showed better noise absorption without an air gap, while multilayer structure 5 effectively absorbed acoustic waves in the presence of a 10 mm air gap. Example 12 Performance evaluation of resistance via stone fragment test of the multilayer structure of the invention. The multilayer structure 5, prepared according to example 9, was tested for its strength properties. The test conditions used were in accordance with global automotive customer specifications. Rocks were loaded into a Gravelometer for launching onto the multi-layered test surfaces. The objective of the experiment is to test the material's resistance to gravel impact, thereby establishing its reliability against corrosion. Therefore, after the rock treatment, there will be no holes, cracks, or spalling in the sample, and no water will flow through it. The conditions for the exposure and fragmentation resistance test were as follows: 10 cycles of 500 g of Basalt (7 rocks) were used at a pressure of 0.4 MPa. The multilayer structure sample was 150 x 100 mm, and the thickness was Lnn / zznz / E / YiAi mm. The angle used for the experiment was 90° and the distance between the launching area and the test specimens was 35 cm. The multilayer structure 5 of the invention showed very good resistance to stone impact. No holes formed after treatment, indicating high rigidity and therefore protection against corrosion, as shown in Figure 5. Example 13 Performance evaluation of resistance via stone fragmentation test of the multilayer structure of the invention The multilayer structure 6 prepared according to example 10 was tested for its strength properties. The test was performed as indicated in Example 12. The multi-layered structure showed very good resistance to stone impact. No holes formed after treatment, indicating high rigidity and therefore protection against corrosion, as shown in Figure 6. It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the following claims are claimed as property:

1. A multilayer structure, characterized in that it comprises: two outer layers a, made of a nonwoven material; at least one intermediate layer β, made of glass wool fiber; at least one intermediate layer of polyurethane γ; wherein the at least one intermediate layer of polyurethane γ is made of polyurethane derived from automotive polyurethane waste and wherein the at least one intermediate layer of polyurethane γ has a density value in the range of 20 to 30 g / L.

2. The multilayer structure according to claim 1, characterized in that the at least one intermediate layer β and / or the at least one intermediate layer γ are repeated, independently of each other, at least twice. 3.The multilayer structure according to claim 1, characterized in that it has the following sequence of layers: 1) an outer layer, made of a non-woven material; reí? Lnn / zznz / E / YiAi. 2) at least one intermediate layer β, of glass wool fiber; 3) at least one intermediate layer of γ polyurethane, manufactured from automotive polyurethane waste and 4) an outer layer, made of a nonwoven material.

4. The multilayer structure according to claim 1, characterized in that it has the following sequence of layers: 1) an outer layer, made of a nonwoven material; 2) at least one intermediate polyurethane layer γ; 3) at least one intermediate layer β, made of glass wool fiber; and 4) an outer layer, made of a nonwoven material.

5. The multilayer structure according to claim 3 or 4, characterized in that layers 2) and 3) are repeated at least twice, independently of each other.

6. The multilayer structure according to any of claims 1-5, characterized in that the at least one intermediate polyurethane layer γ has a density value in the range of 22 to 25 g / L, preferably approximately 22 g / L.

7. The multilayer structure according to any of claims 1-5 Lnn / zznz / E / YiAi of claims 1-6,characterized in that at least one intermediate polyurethane layer γ has a permanent compression deformation in the range of 1000 to 1200 g / cm² (according to DIN EN ISO 1856).

8. The multilayer structure according to any of claims 1-7, characterized in that the at least one intermediate polyurethane layer γ has an elongation at break value in both directions in the range of 40 to 150% (according to EN ISO 9073-3).

9. The multilayer structure according to any of claims 1-8, characterized in that the at least one intermediate polyurethane layer γ has a tear strength in both directions of 14 N / cm² (according to DIN EN ISO 1798).

10. The multilayer structure according to any of claims 1-9,characterized in that the outer layer, made of a nonwoven material, consists of viscose-polyester-PET based fibers coated with a phenolic coating.

11. The multilayer structure according to any of claims 1-9, characterized in that the outer layer, made of a nonwoven material, is a carbon nonwoven material, preferably a CLOTH (pre-oxidized polyacrylonitrile C fibers)-polyester fiber.

12. The multilayer structure according to any of claims 1-11, characterized in that the at least one intermediate β layer of glass wool fiber is bonded with a thermosetting phenolic resin binder (R225) in an amount of 10% relative to the total weight of the β layer, more preferably comprising a flame retardant additive.

13. The multilayer structure according to any of claims 1-12,characterized in that the flexural modulus (E) is in the range of 380 to 1600 N / mm² as measured according to ISO 179, preferably 550-950 N / mm²; the breaking load is in the range of 40 to 80 N as measured according to ISO 179; and the tensile strength is in the range of 4 to 16 N / mm² according to ISO 179.

14. An automotive component, characterized in that it is manufactured from the multilayer structure according to any one of claims 1-13.

15. The automotive component according to claim 13, characterized in that such automotive component is selected from the group consisting of a wheel arch, air ducts, retractable hardtop, trunk floor cover, and underbody cover.

16. A process for preparing the multilayer structure according to any one of claims 1-13.Lnn / zznz / E / YiAi characterized in that it comprises the following steps: a) providing automotive polyurethane waste having a density value in the range of 20 to 30 g / L; b) cutting a glass wool fiber into sheets having a two-dimensional shape suitable for a molding step f), thereby obtaining at least one β-layer sheet made of glass wool fiber; c) cutting the automotive polyurethane waste from step a) into sheets having a two-dimensional shape suitable for a molding step f), thereby obtaining at least one γ-layer sheet made of polyurethane waste having a density value in the range of 20 to 30 g / L; d) cutting a nonwoven material into sheets having a two-dimensional shape twice the two-dimensional shape of the β-layer or γ-layer, thereby obtaining at least one nonwoven sheet; e) folding the at least one nonwoven sheet from step d).thus obtaining two outer layers; f) inserting the β and y layers, from steps b) and e), respectively, between the two outer layers of e), thus obtaining a sandwich assembly; g) loading the sandwich assembly into a heat-molding device; h) molding the assembled sandwich assembly via thermocompression, at a temperature in the range of 190 to 200°C; i) obtaining the multilayer structure of the invention.

17. The process according to claim 16, characterized in that the cutting steps b), c), and d) are performed with at least one blade having a force of 25 kg / mm².

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