Sound-absorbing and sound-insulating automotive noise-attenuating trim component

Abstract

The present invention relates to an automotive sound attenuating trim component having both sound-insulating and sound-absorbing properties. The trim component has mass spring characteristics and thus includes a spring layer and a mass layer. The mass layer is composed of a barrier layer and a porous fiber layer adjacent to each other and is laminated with the barrier layer located between the spring layer and the porous fiber layer, the radiation frequency of the mass layer is at least 3 kHz, and the average sound absorption value is at least 0.40.

Description

Technical Field

[0001] This invention relates to the field of automotive trim components installed inside and / or outside road vehicles to improve the acoustic comfort of occupants. Background Technology

[0002] There are several noise sources in road vehicles that can radiate noise over a very wide frequency range, typically from at least 100 Hz to 10 kHz. This can cause discomfort to passengers because this frequency range covers most of the audible frequency range.

[0003] Noise-reducing trim components for improving the acoustic comfort of occupants in road vehicles are known in the art. These components can be fitted onto body panels to cover at least a portion of the surface of these panels. An example of such noise-reducing trim components is an interior dashboard partition, typically mounted on the firewall of a vehicle body and substantially covering its entire surface. In other cases, noise-reducing trim components may not be fitted onto body panels but are instead mounted directly onto the noise source, at least covering a portion of that noise source. An example of such noise-reducing trim components is an engine cover, typically mounted directly onto the vehicle engine and covering its upper area.

[0004] The two examples above both pertain to components whose primary purpose is to attenuate noise radiated by the powertrain. However, in road vehicles, several noise-attenuating decorative components can typically be found to address other noise sources. Examples include carpet insulation and wheel arch insulation, primarily used to attenuate noise radiated by the tires.

[0005] Noise-attenuating decorative components function due to their sound-absorbing and / or sound-insulating properties. Sound insulation refers to the ability of a noise-attenuating decorative component to reflect the sound energy carried by sound waves impacting it. Sound absorption refers to the ability of a noise-attenuating decorative component to dissipate the sound energy carried by sound waves impacting it internally.

[0006] When installed in road vehicles, both sound absorption and sound insulation contribute to the acoustic performance of noise-attenuating trim components. Therefore, it is desirable for noise-attenuating trim components to possess both sound insulation and sound absorption properties. However, the contribution of sound insulation and / or sound absorption to the acoustic performance of noise-attenuating trim components may depend on the frequency.

[0007] Typically, sound insulation contributes to the acoustic effectiveness of noise-reducing trim pieces only up to approximately 3 kHz, particularly between 800 Hz and 3 kHz. Side paths above 3 kHz that may not be intercepted by noise-reducing trim pieces mounted on body panels and / or around noise sources can consequently contribute to noise transmission into the passenger compartment of on-road vehicles. On the other hand, sound absorption typically contributes to the acoustic effectiveness of noise-reducing trim pieces only above approximately 800 Hz. Sound absorption below 800 Hz is generally minimal because encapsulation limitations usually restrict the thickness of the trim pieces. The frequency range between 800 Hz and 3 kHz represents the range where both sound insulation and sound absorption are likely important for the effectiveness of noise-reducing trim pieces when installed in a vehicle.

[0008] EP2684187 discloses an example of a noise-attenuating decorative component that possesses both sound insulation and sound absorption properties. Specifically, this document discloses a noise-attenuating decorative component comprising a sound-insulating region and a sound-absorbing region. The sound-insulating region exhibits good sound insulation performance. On the other hand, the sound-absorbing region exhibits good sound absorption performance.

[0009] More specifically, according to the disclosure of EP2684187, the sound-insulating region has acoustic mass spring characteristics, and it comprises a decoupling layer and a mass layer, wherein the mass layer is achieved by means of a porous fiber layer backed by a barrier layer. In the sound-insulating region, the porous fiber layer is compressed to have at least the following compressive dynamic Young's modulus:

[0010] Where T p It is the thickness of the porous fiber layer, in mm (AW). p It is the area weight of the porous fiber layer, in g / m². 2 And AW b It is the area weight of the barrier, in g / m². 2 On the other hand, the sound-absorbing region includes at least a portion of the porous fiber layer in the sound-insulating region; however, the thickness of the portion of the porous fiber layer in the sound-absorbing region is greater than the thickness of the portion of the porous fiber layer in the sound-insulating region.

[0011] While the noise-reducing decorative components disclosed in EP2684187 do combine sound insulation and sound absorption properties, the way this combination is achieved is not optimal and also brings some practical problems.

[0012] First, in such components, the sound-insulating area has poor or no sound-absorbing performance because the porous fiber layer must be heavily compressed to achieve the desired dynamic Young's modulus of compression. Simultaneously, the sound-absorbing area also has poor or no sound-insulating performance because the porous fiber layer must be thickened to achieve the desired absorption performance, and therefore, even when combined with a backing barrier layer, it may not function as a mass layer. Thus, in noise-reducing decorative components according to EP2684187, the sound-insulating and sound-absorbing areas are separate, with the sound-insulating area exhibiting poor or no sound-absorbing performance, and the sound-absorbing area exhibiting poor or no sound-insulating performance. This fact inevitably limits the acoustic performance of the component when installed in a vehicle.

[0013] In addition, achieving noise reduction decorative components according to EP2684187 may require porous fiber layers of variable thickness, which makes the design, manufacturing process and required tools of the components complex and expensive.

[0014] Therefore, the object of this invention is to provide a solution to these problems in the prior art. With the invention provided herein, a noise-reducing decorative component can be obtained that optimally combines sound insulation and sound absorption, and can be designed and manufactured in a simple and cost-effective manner. Summary of the Invention

[0015] The object of the present invention is achieved by the noise-attenuating decorative component according to claim 1 and the manufacturing method according to claim 14.

[0016] In its main aspect, the present invention relates to a sound-attenuating decorative component comprising at least one region having mass spring characteristics, the region comprising a spring layer and a mass layer. In the sound-attenuating decorative component according to the invention, the mass layer consists of a barrier layer and a porous fiber layer that are adjacent to each other and laminated together, wherein the barrier layer is located between the spring layer and the porous fiber layer. Furthermore, in the sound-attenuating decorative component according to the invention, the mass layer has a radiation frequency of at least 3 kHz and an average sound absorption value of at least 0.40.

[0017] Surprisingly, it was found that the acoustic performance of the sound-attenuating decorative component according to the present invention is significantly enhanced compared to prior art solutions. This is attributed to the fact that the sound-attenuating decorative component includes at least one region that provides excellent sound insulation and excellent sound absorption performance. The excellent sound insulation performance of this region stems from the combination of its mass spring characteristics and a mass layer with a radiation frequency of at least 3 kHz. Simultaneously, its excellent sound absorption performance arises from its average sound absorption value of at least 0.40. Compared to prior art solutions, the component according to the present invention represents a substantial advancement, wherein the sound absorption and sound insulation performance are confined to a separate region of the component, rather than combined within the same region, a fact that limits the acoustic performance of these prior art solutions.

[0018] The "radiation frequency" of the mass layer, composed of adjacent and laminated barrier layers and porous fiber layers, is a specific frequency that can be evaluated using the following formula:

[0019] Among them AW p It is the area weight of the porous fiber layer, in kg / m². 2 AW b It is the area weight of the barrier layer, in kg / m². 2 T p It is the thickness of the porous fiber layer, in meters (m), and E p It is the compressive dynamic Young's modulus of the porous fiber layer, expressed in Pa. It is clear from the formula that the radiation frequency of the mass layer, composed of the adjacent and laminated barrier layer and the porous fiber layer, depends only on the physical properties of these layers, and not on the physical properties of the other layers in the sound-attenuating decorative component that includes the mass layer.

[0020] At the radiation frequency, a mass layer consisting of porous fiber layers and barrier layers that are adjacent to each other and laminated together can radiate noise very effectively, and this can impair the noise insulation of a sound-attenuating decorative component that has mass spring characteristics and includes such a mass layer, especially at the radiation frequency of the mass layer and in the frequency range around it.

[0021] Here, a "layer" is a body composed of one or more materials and is comprised between two closely spaced surfaces, where the distance between the surfaces is much smaller than their dimensions. These two surfaces are referred to as the "sides" of the layer, and they are opposite each other. The distance between the two surfaces is represented by the thickness of the layer, which can be variable. In particular, a "barrier layer" is an airtight or gas-impermeable layer, meaning that air is not allowed to enter it.

[0022] In the mass layer according to the invention, the radiation frequency is advantageously above 3 kHz, within which the degradation of the sound insulation performance of the noise-attenuating trim element according to the invention has a limited impact on its acoustic effect. In fact, above 3 kHz, the transmission of noise into the passenger compartment of a road vehicle is typically strongly influenced by side paths that may not be intercepted by the noise-attenuating trim element installed around the body panels and / or noise sources, thus limiting the relevance of sound insulation to the acoustic effect of the noise-attenuating trim element installed in the vehicle.

[0023] The out-of-plane dynamic Young's modulus is measured along the thickness direction of the porous fiber layer, hereinafter referred to as the "out-of-plane" direction. The out-of-plane dynamic Young's modulus of the porous fiber layer can be measured using a commercially available "Elwis-S" system. It is noteworthy that the out-of-plane dynamic Young's modulus of the porous fiber layer is not frequency-dependent. Therefore, sufficient engineering accuracy can be obtained by measuring at any frequency. Preferably, it is obtained by averaging over a frequency range (e.g., between 300 Hz and 700 Hz) to compensate for unavoidable small frequency variations due to inaccuracies in the measurement process.

[0024] The compressive dynamic Young's modulus of a porous fiber layer can be measured by extracting one or more samples from one or more regions of the same porous fiber layer, where the component is relatively flat. The standard test using the Elwis-S system is performed on a circular sample with a diameter of 100 mm. However, if a relatively flat sample of this diameter cannot be extracted from the sound-attenuating decorative component, the test can also be performed on a sample with a smaller diameter. Preferably, the sample diameter should be at least 60 mm.

[0025] Furthermore, the load mass used for the Elwis-S test should ensure that the sample under test is properly loaded and uniformly excited on all its surfaces. For testing with a standard circular sample with a diameter of 100 mm, a load mass between 800 g and 1300 g is preferably used. For testing with circular samples of different diameters, the top load mass should be readjusted according to the sample surface.

[0026] The average sound absorption of one or more sound-absorbing layers is the frequency average of its absorption coefficient between 800 Hz and 6.3 kHz, measured according to ISO 10534-2:1998 and expressed in one-third octave bands. Studies have found this quantity particularly suitable for defining the impact of the sound absorption performance of trim components on the acoustic effects when installed in a car. This may be related to the fact that the frequency range indicated by the A-weighted curve, conventionally used in acoustics to illustrate human ear sensitivity, is the range of frequencies to which the human ear is most sensitive. In fact, it is precisely within this frequency range that the level of the A-weighted curve is approximately -1 dB higher.

[0027] In particular, for the mass layer according to the invention, the average sound absorption is advantageously at least 0.4, which ensures that the sound absorption of the sound attenuation trim according to the invention can substantially contribute to the in-vehicle acoustic efficiency of the trim in the range of frequencies most sensitive to the human ear, unlike noise attenuation trim in the prior art.

[0028] The average sound absorption of the mass layer can be measured by extracting one or more samples from the same porous fiber layer from one or more areas of a sound-attenuating decorative component, where the component is relatively flat. Standard measurements of the average sound absorption are taken from samples with diameters of 60 mm and 29 mm. Generally, it is not difficult to find one or more relatively flat areas on the sound-attenuating decorative component and extract samples of this size from them. The average sound absorption of the mass layer is measured from the side of the porous fiber layer.

[0029] As can be seen from all of the above, the mass layer according to the invention combines the best combination of sound insulation and sound absorption properties in at least one area of ​​the sound attenuation decorative component according to the invention, and can significantly improve the in-vehicle acoustic effect of the same decorative component compared with prior art solutions.

[0030] This is due to at least one region possessing mass spring characteristics, comprising a spring layer and a mass layer, wherein the mass layer consists of adjacent barrier layers and porous fiber layers, with the barrier layers located between the spring layer and the porous fiber layers, wherein the mass layer has a radiation frequency of at least 3 kHz, and the porous fiber layers have an average sound absorption value of at least 0.40. To further enhance the acoustic effect of the sound-attenuating decorative component according to the invention, preferably, the at least one region covers at least 50% of the surface of the decorative component according to the invention, more preferably at least 70%, and even more preferably at least 85%. Increasing the coverage of the at least one region effectively results in an improvement in the in-vehicle acoustic efficiency of the sound-attenuating decorative component according to the invention.

[0031] The massing layer according to the invention comprises adjacent porous fiber layers and a barrier layer. The porous fiber layers according to the invention can be very light and thin, which is advantageous because it helps limit the weight of the decorative component according to the invention and the required packaging space. Preferably, the areal weight of the porous fiber layer according to the invention is 500 g / m². 2 and 2000g / m 2 Between, more preferably between 800g / m 2 and 1800g / m 2 Between, or even more preferably at, 1000 g / m 2 and 1500g / m 2 Furthermore, the thickness of the porous fiber layer according to the present invention is preferably between 2 mm and 10 mm, more preferably between 3 mm and 8 mm, and even more preferably between 4 mm and 7 mm.

[0032] Furthermore, the density of the porous fiber layer according to the present invention is preferably 100 kg / m³. 3 and 600kg / m 3 Between, more preferably between 200 kg / m 3 and 400kg / m 3 Between, or even more preferably at, 250 kg / m 3 and 350kg / m 3 The higher the density of the porous fiber layer according to the invention, the higher its dynamic Young's modulus of compression, and therefore its radiation frequency. Therefore, a high-density porous fiber layer is ideal. However, besides increasing the weight of the sound-attenuating decorative component according to the invention, increasing the density of the porous fiber layer may make its production more difficult, as this leads to a significant increase in the force required to compress the porous fiber layer.

[0033] The areal weight and thickness of the porous fiber layer according to the invention can vary on its surface, as long as this does not impair the fundamental characteristics of the mass layer according to the invention. However, preferably, the porous fiber layer according to the invention has a substantially constant thickness and a substantially constant areal weight across its entire surface. This can be advantageous because a porous fiber layer with a substantially constant areal weight and thickness simplifies the design and production process of the sound-attenuating decorative component according to the invention, and it requires less expensive tools. Here, "substantially constant" means that the thickness and / or areal weight of the porous fiber layer can vary point-to-point, corresponding to variations in typical production tolerances, without affecting the fundamental characteristics of the mass layer according to the invention. For example, a porous fiber layer whose thickness varies on its surface by 10% or less relative to its average value, such as 5.0 mm + / - 0.5 mm, can be considered to have a substantially constant thickness because such thickness variation corresponds to typical production tolerances and has little effect on the radiating frequency of the mass layer according to the invention and the average sound absorption value of the same porous fiber layer according to the invention. Similarly, and for the same reason, for example, the areal weight of the porous fiber layer on its surface varies with its average value by less than 5%, such as 1500 g / m². 2 + / - 75g / m 2 It can be considered to have a substantially constant area weight.

[0034] The porous fiber layer can comprise any kind of natural and / or synthetic fiber commonly found in industry. Examples of natural fibers include cotton, wool, flax, hemp, bamboo, sisal, jute, and abaca fibers. Examples of synthetic fibers are polypropylene fibers, polyethylene fibers, polyester fibers such as polyethylene terephthalate (PET) fibers, polylactic acid (PLA) fibers, and polyamide (PA) fibers, particularly polyamide 6 or polyamide 6.6 fibers. Synthetic fibers can be monocomponent or bicomponent fibers. Monocomponent fibers are made from a single material, while bicomponent fibers are synthetic fibers made from two polymers with different chemical and / or physical structures, tightly bonded together along the fiber length. Bicomponent fibers can be produced using processes known in the art, such as melt spinning. The porous fiber layer can consist of only one type of fiber, but can also be a mixture of different types of fibers.

[0035] Advantageously, the fibers of the porous fiber layer according to the invention can be at least partially recyclable to reduce the environmental impact of the manufacturing process of the sound-attenuating decorative component according to the invention, particularly in terms of material consumption. Specifically, the fibers of the porous fiber layer can be at least partially in the form of regenerated natural fibers, such as regenerated cotton fibers, or in the form of regenerated synthetic fibers, such as regenerated polyester fibers. A regenerated fiber is defined as a recyclable fiber containing at least 51% by weight of the relevant material. Thus, for example, regenerated cotton fiber contains at least 51% by weight of recycled cotton fibers, with the remaining 49% by weight consisting of fibers of different materials and / or virgin fibers. Preferably, the porous fiber layer according to the invention contains at least 50% by weight, more preferably at least 65% by weight, and even more preferably at least 80% by weight of fibers in the form of regenerated natural fibers and / or regenerated synthetic fibers.

[0036] Furthermore, the porous fiber layer according to the invention preferably contains an adhesive, the amount of which is preferably between 10% and 50% by weight, and even more preferably between 20% and 40% by weight. The adhesive can be thermosetting or thermoplastic. In both cases, some form of heat treatment is required to activate it. Due to the adhesive, during the production process of the sound-attenuating decorative part according to the invention, the fibers of the porous fiber layer can be firmly bonded together along the entire length of the fiber while the decorative part is molded into the desired shape. This type of bonding process ensures that the porous fiber layer stably and permanently maintains the desired shape at the end of the process. Thermosetting adhesives are preferred when enhanced mechanical properties and structural consistency are required. On the other hand, thermoplastic adhesives in fiber form are preferred when very complex three-dimensional shapes must be achieved.

[0037] Thermosetting adhesives are preferably in the form of epoxy resins or phenolic resins or mixtures thereof. Thermoplastic adhesives are preferably in the form of thermoplastic adhesive fibers. These are fibers comprising at least a portion that melts due to heat treatment, forming droplets that bond all other fibers at their intersections / contact points. The melting temperature of the adhesive fiber (or the molten portion of the adhesive fiber) must be significantly lower than the melting temperature of all other fibers (and the possibly unmelted portions of the adhesive fiber). The adhesive fiber can be a single-component fiber or a bicomponent fiber. Particularly preferred thermoplastic adhesive fibers are thermoplastic bicomponent core-sheath adhesive fibers. Thermoplastic bicomponent core-sheath adhesive fibers are bicomponent fibers in which one of the two components (sheath) surrounds the other (core). The sheath component is the portion of the fiber that melts during the heat treatment described above. Also in bicomponent core-sheath adhesive fibers, the first polymer is preferably polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), and the second polymer is preferably a copolymer of poly(butylene terephthalate) (coPET) or a copolymer of polybutylene terephthalate (coPBT).

[0038] The fibers constituting the porous fiber layer can be short fibers and filaments. This also applies to the case where thermoplastic adhesive fibers can be included in the porous fiber layer according to the invention. Short fibers are fibers different from filaments and have discrete predetermined lengths. In particular, the short fibers included in the porous fiber layer preferably have a length between 32 mm and 76 mm.

[0039] The fineness of the fibers constituting the porous fiber layer is preferably between 0.5 denier and 10 denier, more preferably between 0.5 denier and 5 denier. For a given mass of porous fiber material, finer fibers provide better sound absorption performance.

[0040] According to the present invention, the porous fiber layer is preferably manufactured by first preparing a fibrous nonwoven in the form of a cushion, which is composed of fibers of the desired fiber composition (hereinafter referred to as "semi-finished product" or simply "semi-finished product"), and then subjecting it to heat compression.

[0041] The production of the semi-finished product can be carried out according to any process known in the art. Such a process may specifically include the step of forming a fiber web composed of randomly oriented and unbonded fibers of a desired composition, and the step of consolidating the fiber web. In addition to these two steps, the production of the semi-finished product may also involve other steps, such as carding and cross-lapping, which can be considered to provide a specific preferred orientation for the fibers forming the web.

[0042] The process steps for forming a fiber web composed of randomly oriented and unbonded fibers of the desired composition can be performed using techniques known in the art, such as air-blowing, wet spinning, spun web formation, meltblowing, and electrospinning. The main objective of this step is to obtain a mixture of randomly oriented unbonded fibers with the desired composition, which is as homogeneous as possible.

[0043] The process steps for consolidating the aforementioned fiber web can also be carried out using bonding techniques known in the art, such as thermal bonding, chemical bonding, mechanical bonding, or combinations thereof. Examples of thermal bonding are hot calendering and / or ultrasonic bonding. Examples of chemical bonding are resin / powder coating bonding and / or foam bonding. Examples of mechanical bonding are needle punching and / or hydroentangling. The main purpose of this step is to loosely bond the fibers of the fiber web in the semi-finished product to each other, such bonding provides the semi-finished product itself only with the consistency required to handle it during the production process of the sound-attenuating decorative component according to the invention, while maintaining the semi-finished product in a cushioned form. Therefore, the loose bonding of the fiber portions in the semi-finished product is very different from the completely and firmly bonded bonding of the fibers that occurs during the production process of the aforementioned sound-attenuating decorative component.

[0044] However, it is quite surprising that the bonding technique used for the fiber web in the consolidation semi-finished product was found to affect the characteristics of the porous fiber layer according to the invention, and this was caused by the thermal compression of such semi-finished products.

[0045] Preferably, the consolidation process steps for producing the semi-finished product of the porous fiber layer according to the invention include at least one needle-punching step. Surprisingly, it has been found that, compared to using other bonding techniques to consolidate the porous fiber web of the semi-finished product, the needle-punched semi-finished product, by compressing it to a smaller degree, can achieve the required compressive dynamic Young's modulus for the porous fiber layer. Therefore, by using the needle-punched semi-finished product for production, the porous fiber layer according to the invention can be more easily tuned so that the mass layer according to the invention simultaneously has a radiation frequency above 3 kHz and an average sound absorption value of at least 0.4. In fact, a higher compressive dynamic Young's modulus of the porous fiber layer generally favors a higher radiation frequency of the mass layer according to the invention, while a thicker porous fiber layer generally favors higher sound absorption of the mass layer according to the invention.

[0046] To further enhance the aforementioned advantageous effects, the stitch density of the needled semi-finished product used for producing the porous fiber layer according to the present invention is at least 35 stitches / cm. 2 More preferably at least 40 stitches / cm 2 Even more preferably, at least 50 stitches / cm 2 .

[0047] The needle-punching process can be performed from one or both sides of the semi-finished product. If it is performed from both sides, the needle density mentioned above is the total needle density. Furthermore, the needle density mentioned above can refer not only to the semi-finished product used to produce the porous fiber layer according to the invention by thermal compression, but also to the same porous fiber layer. When compressed into the desired shape of the porous fiber layer according to the invention, the semi-finished product can be slightly stretched, but the stretching will not substantially change the needle density per centimeter. 2 The needle density is represented by this. Therefore, the needle density can also be evaluated on the final porous fiber layer.

[0048] It is important to point out that while the consolidation process steps for producing the semi-finished product of the porous fiber layer according to the invention are considered herein to preferably include at least one needle-punching step, this is not strictly necessary for the implementation of the invention. As is known in the art, other bonding techniques, such as thermal bonding and / or chemical bonding, can be used for the consolidation of the semi-finished product.

[0049] In a first preferred embodiment of the porous fiber layer according to the invention, the porous fiber layer is obtained by heat-compressed airflow forming a web-like needle-punched semi-finished product (i.e., a semi-finished product), wherein the web-forming step is performed by means of an airflow web-forming process, and the web-consolidation step includes a needle-punching process. Preferably, the needle density of the needle-punching process is at least 35 needles / cm. 2 More preferably at least 40 stitches / cm 2 Even more preferably, at least 50 stitches / cm 2 Preferably, in a first embodiment of the porous fiber layer, the semi-finished product (and the resulting porous fiber layer) comprises a mixture of recycled cotton fibers and thermoplastic bicomponent adhesive fibers. In this embodiment, the amount of recycled cotton fibers is preferably 60% to 90% by weight, more preferably 70% to 85% by weight, and the amount of thermoplastic bicomponent adhesive fibers is preferably 10% to 40% by weight, more preferably 15% to 30% by weight. The thermoplastic bicomponent adhesive fibers are preferably PET / CoPET fibers.

[0050] This first preferred embodiment is advantageous in at least two ways. First, because it contains recycled cotton fibers in the fiber blend, which includes a significant amount of recyclable material, this reduces the carbon dioxide footprint of the sound-attenuating decorative component according to the invention, particularly in terms of material consumption. Second, the semi-finished product is obtained through a particularly simple process that does not involve any carding and / or cross-lapping. This makes it easy and cost-effective to produce the semi-finished product using a relatively simple nonwoven production line.

[0051] In a second preferred embodiment, the porous fiber layer according to the invention is substantially composed of thermoplastic bicomponent filaments, which are composed of a first polymer having a higher melting temperature and a second polymer having a lower melting temperature. The filaments preferably have a core-sheath structure. However, other structures known in the art, such as "side-by-side" or "island-in-the-sea" structures, are also possible. The filaments, hereinafter also referred to as "long filaments," are continuous fibers of indefinite length, i.e., unlike short fibers which are cut to a specific length. In this preferred embodiment, the porous fiber layer according to the invention is preferably obtained by heat processing and compression of a semi-finished product consisting of a spun, carded, and cross-laminated fiber web, followed by consolidation by means of a needle-punching process.

[0052] In thermoplastic bicomponent filaments, the melting point of the second polymer is lower than that of the first polymer, therefore, the first and second polymers react differently when the bicomponent fibers are heated. When the bicomponent filaments are heated to a temperature above the softening or melting point of the second polymer (e.g., the sheath polymer in a sheath-core structure) but below the melting point of the first polymer (e.g., the core polymer in a sheath-core structure), the second polymer softens or melts, while the first polymer does not. The softening of the second polymer causes it to become sticky and bind to the filaments, which may be very close together. Simultaneously, the melting of the second polymer causes droplets to form at the intersections of adjacent fibers, binding adjacent fibers together, while the first polymer remains intact, forming a network of solid, long filaments in the final porous fiber layer.

[0053] In this embodiment, the porous fiber layer according to the invention exhibits excellent mechanical properties, stemming from the synergistic effect between the filamentary nature and the bicomponent properties of the filaments. On one hand, the filaments span the entire surface of the porous fiber layer. On the other hand, the melting of the second polymer ensures the formation of bonding points between the filaments, which are uniformly distributed along the entire length of the filaments themselves. As a result, a network of filaments spans the entire surface of the porous fiber layer according to the invention and is tightly linked to each other. This network exhibits excellent mechanical properties, particularly in terms of flexural stiffness. The amount of the second polymer relative to the weight of the porous fiber structure layer is preferably 10% to 50% by weight, more preferably 20% to 40% by weight, to improve the bonding between the filaments.

[0054] Due to its excellent mechanical properties, the second embodiment of the porous fiber layer may be particularly suitable for applications where the sound attenuation decorative component according to the invention may be subjected to high levels of mechanical stress or vibration, such as powertrain enclosures, engine hoods, trunk floor plates, and wheel arch liners.

[0055] In this embodiment, the porous fiber layer according to the invention preferably has a flexural modulus of at least 70 MPa, measured according to ISO 178:2019 at 23 degrees Celsius and 50% relative humidity, preferably between 70 MPa and 1300 MPa, more preferably between 100 MPa and 950 MPa, and more preferably between 150 MPa and 700 MPa, so that no substantial deformation will occur under structural loads.

[0056] In a particularly preferred implementation of this embodiment, the filaments are composed of terephthalate-based polyester. The porous fiber layer, primarily composed of terephthalate-based polyester, facilitates recycling. In this embodiment, the first polymer (i.e., a polymer with a higher melting point) is preferably polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), and the second polymer (i.e., a polymer with a lower melting point) is preferably a copolymer of polyethylene terephthalate (coPET) or a copolymer of polybutylene terephthalate (coPBT). Again in this embodiment, at least a portion of the polyester can advantageously have recyclable properties. For example, the PET used as the first polymer can be obtained from consumer products such as PET flakes, from PET packaging articles, or from PET marine products (like fishing nets), by melting them and forming granules that can be used in the spinning process. The advantage of using recyclable polyester is a reduction in the environmental impact of the manufacturing process of the waterproof cover according to the invention, particularly its carbon dioxide footprint. In this embodiment, the polyester used for the bicomponent fiber is preferably at least 20%, more preferably at least 50%, and even more preferably at least 70% of recyclable polyester, wherein the percentage is a weight percentage calculated relative to the total weight of the porous fiber structure layer.

[0057] When they are composed of polyester, the diameter of the bicomponent filaments is preferably between 14 micrometers and 37 micrometers, more preferably between 20 micrometers and 25 micrometers, to achieve the required strength.

[0058] In a third preferred embodiment, the porous fiber layer according to the invention is substantially composed of a fiber mixture comprising 20% ​​to 50% by weight of PET monocomponent short fibers, 20% to 50% by weight of thermoplastic bicomponent PET / CoPET adhesive short fibers, and 20% to 40% by weight of hollow composite monocomponent PET fibers. In this preferred embodiment, the porous fiber layer according to the invention is obtained by heat-processing a semi-finished product consisting of an air-laid fiber web having the above-described fiber composition and consolidating it by thermal bonding (e.g., by hot calendering).

[0059] Similar to the second preferred embodiment described above for porous fiber layers, this third preferred embodiment is particularly advantageous in terms of recyclability because it is 100% PET. Furthermore, the presence of hollow composite fibers in the fiber mixture makes it exceptionally lightweight and improves its sound absorption properties.

[0060] Similar to the previous description of the second preferred embodiment for porous fiber layers, PET with different components of the fiber mixture can advantageously have recyclable properties.

[0061] The mass layer according to the invention consists of adjacent porous fiber layers and a barrier layer. The barrier layer can be composed of any one or more materials, as long as it fulfills its primary function, namely, as an acoustic barrier.

[0062] The areal weight and material of the barrier layer are likely important features in the design of the sound-attenuating decorative component according to the invention. Indeed, those skilled in the art can advantageously adjust the areal weight and material of the barrier layer to achieve a desired trade-off between the weight of the sound-attenuating decorative component and its sound insulation. A greater areal weight of the barrier layer enhances the sound insulation of the sound-attenuating decorative component according to the invention, particularly in the frequency range between 800 Hz and 3 kHz. However, at the same time, it makes the component heavier, which is detrimental to the fuel consumption and CO2 emissions of the vehicle in which the component is ultimately installed.

[0063] When a particularly lightweight sound-attenuating decorative component is required, the areal weight of the barrier layer is preferably 10 g / m². 2 and 200g / m 2 Between, more preferably between 50g / m 2 and 150g / m 2 between.

[0064] In this case, a preferred embodiment of the barrier layer according to the invention is a polymeric membrane, preferably comprising at least one polymer or copolymer selected from: polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT); polyamides such as polyamide 6 or polyamide 66; polyolefins such as polypropylene (PP) or polyethylene (PE); thermoplastic elastomers (TPEs such as thermoplastic polyolefins (TPO) or thermoplastic polyurethanes (TPU); elastomers such as EPDM-based elastomers or butadiene-based elastomers, or silicones; high-performance polymers such as polytetrafluoroethylene (PTFE), polyetherimide, polysulfone, polyethersulfone, or polyetheretherketone (PEEK); ethylene vinyl acetate (EVA); and biopolymers such as polylactic acid (PLA).

[0065] Preferably, the material or materials used for the membrane and the material or materials used for the porous fiber layer belong to the same chemical category, making recycling easier.

[0066] The membrane can be single-layer, double-layer, or multi-layer. Double-layer or multi-layer membranes can be used to further improve stability, elasticity, and / or robustness.

[0067] In this embodiment of the barrier layer according to the invention, the membrane preferably has a tensile strength at break greater than 20 MPa and a strain at break greater than 100%. If the membrane is anisotropic, these values ​​refer to both the machine direction and the cross direction. Stress and strain at break are measured according to ISO 527-1:2019 and 527-3:2018. Furthermore, the membrane thickness is preferably between 10 micrometers and 200 micrometers, more preferably between 50 micrometers and 150 micrometers.

[0068] On the other hand, when a sound-attenuating decorative component with particularly enhanced sound insulation is required, the area weight of the barrier layer is preferably 500 g / m². 2 and 8000g / m 2 Between, more preferably between 1500g / m 2 and 5000g / m 2 Between, and even more preferably at 2000 g / m 2 and 3500g / m 2 between.

[0069] In this context, a preferred embodiment of the barrier layer according to the invention is a layer comprising a matrix of thermoplastic elastomer material, which is substantially loaded with inorganic fillers. In the art, such a layer is often referred to as a "thick layer," and because it is airtight, it is suitable for use as a barrier layer in a sound-attenuating decorative component according to the invention.

[0070] In this embodiment of the barrier layer according to the invention, the thermoplastic elastomer matrix comprises one or more materials preferably selected from the group consisting of: ethylene-vinyl acetate copolymer (EVA); ethylene propylene diene monomer (EPDM); polyester, such as polyethylene terephthalate (PET) and / or polybutylene terephthalate (PBT); polypropylene (PP); polyethylene, such as high-density polyethylene (HDPE) and / or low-density polyethylene (LDPE) and / or ultra-high molecular weight polyethylene (UHMWPE); polyvinyl chloride (PVC); polycarbonate (PC); polyamide, such as PA-4 and / or PA-6 and / or PAA-66; thermoplastic polyimide (TPI); thermoplastic polyolefin (TPO); thermoplastic polyurethane (TPU); polytetrafluoroethylene (PTFE); polyetheretherketone (PEEK); acrylonitrile-butadiene-styrene (ABS); polymethyl methacrylate (PMMA). The inorganic filler is preferably one of calcium carbonate (CaCO3) and / or barium sulfate (BaSO4). Furthermore, the amount of inorganic filler is preferably up to about 85% by weight.

[0071] In this embodiment of the barrier layer according to the present invention, the thickness of the barrier layer is preferably between 0.2 mm and 5 mm, and more preferably between 0.8 mm and 3 mm.

[0072] The choice of the barrier layer, particularly its area weight and material, may depend on an ideal trade-off between the sound insulation performance and total weight of the sound-attenuating decorative component according to the invention. Furthermore, this may also depend on the material of the porous fiber layer. Preferably, one or more materials of the barrier layer and one or more materials of the porous fiber layer belong at least partially to the same chemical class. This facilitates the process of laminating the porous fiber layer and the barrier layer together. In fact, for the sound-attenuating decorative component according to the invention to achieve the desired effect, the barrier layer and the porous fiber layer must be adjacent to each other and laminated together. Here, "laminated together" means that they are permanently assembled in such a way that they together serve as a mass layer under the action of sound waves impacting the sound-attenuating decorative component according to the invention. The lamination process can be carried out, for example, by heating and / or pressurizing and / or welding and / or adhesion.

[0073] In addition to the aforementioned advantages in the lamination process, the fact that one or more materials of the barrier layer and one or more materials of the porous fiber material layer belong at least partially to the same chemical class also contributes to the recyclability of the sound attenuation decorative component according to the invention.

[0074] In the sound attenuation decorative component according to the invention, the spring layer has the function of isolating the mass layer from the sound waves and / or vibrations of the noise source.

[0075] Preferably, the dynamic compression Young's modulus of the spring layer is not higher than 300 kPa, more preferably not higher than 150 kPa, and even more preferably not exceeding 80 kPa. Furthermore, the thickness of the spring layer is preferably between 1 mm and 80 mm, more preferably between 3 mm and 50 mm, and even more preferably between 5 mm and 40 mm. Generally, a lower dynamic compression Young's modulus and a higher thickness can provide better performance, i.e., the spring layer better isolates the mass layer from the sound waves and / or vibrations of noise sources. However, in practical situations, the thickness may be limited by design constraints, such as packaging space or cost.

[0076] The dynamic compressive Young's modulus of the spring layer can be measured using the commercially available Elwis-S tool in a manner similar to that described previously for porous fiber layers according to the invention. However, in the case of the spring layer, a load mass between 150 g and 400 g is preferred for the Elwis-S test. This load mass value refers to a standard circular sample with a diameter of 100 mm. For samples of different sizes, the load mass must be readjusted as previously described.

[0077] In the sound-attenuating decorative component according to the invention, the spring layer may comprise any material, as long as it fulfills the aforementioned main functions. Preferably, it comprises porous and / or honeycomb materials, which is advantageous in terms of weight reduction.

[0078] In a first preferred embodiment, the spring layer according to the invention is composed of a nonwoven fiber. In this embodiment, the fiber material used for the spring layer is substantially the same as the fiber material used for the porous fiber layer according to the invention and previously described. However, the spring layer preferably has a lower density than the porous fiber layer according to the invention, i.e., it is preferably more fluffy and less compressed, as this enhances its noise / vibration isolation function against noise sources. In this embodiment, the density of the spring layer is preferably 30 kg / m³. 3 and 300kg / m 3 Between, more preferably between 40 kg / m 3 and 200kg / m 3 Between, or even more preferably at 50 kg / m 3 and 150kg / m 3 between.

[0079] The first preferred embodiment of the spring layer according to the invention can provide advantages in terms of the recyclability of the sound attenuation decorative component according to the invention, especially when one or more materials of the spring layer belong to the same chemical class as one or more materials of the barrier layer and the porous fiber layer.

[0080] In a second preferred embodiment, the spring layer according to the invention is composed of open-cell foam, preferably polyurethane foam. In this embodiment, the density of the foam is preferably 30 kg / m³. 3 and 200kg / m 2 Between, more preferably between 40 kg / m 3 and 120kg / m 3 Between, or even more preferably at 50 kg / m 3 and 90kg / m 3Between. This implementation of the spring layer can be advantageous because the foam, particularly polyurethane foam, offers excellent molding possibilities and greater design flexibility. Therefore, this embodiment may be advantageous if the sound-absorbing decorative component according to the invention is to be installed on a vehicle body panel and / or noise source with a particularly complex three-dimensional shape.

[0081] Those skilled in the art can advantageously combine all the above-described preferred embodiments of the porous fiber layer, barrier layer, and spring layer according to the invention, based on the desired trade-offs between in-vehicle acoustic efficiency, weight, process complexity, and design constraints.

[0082] For example, the mass layer according to the invention can be obtained by combining a porous fiber layer (composed of an air-laid needle-punched porous fiber layer, including regenerated cotton fibers and adhesive short fibers) of the first preferred embodiment described above with a barrier layer composed of a thick layer of EPDM, the porous fiber layer being suitably tuned to have a radiation frequency higher than 3 kHz and an average sound absorption value of at least 0.4. Furthermore, this mass layer according to the invention can be combined with a spring layer made of foam to obtain an embodiment of a sound-attenuating decorative component according to the invention, which has excellent sound insulation performance and is suitable for installation on vehicle panels and / or noise sources with complex three-dimensional shapes.

[0083] Similarly, the mass layer according to the invention can be achieved by combining a porous fiber layer (composed of thermoplastic bicomponent filaments, preferably PET thermoplastic bicomponent filaments) of the previously described second preferred embodiment with a lightweight PET film (e.g., 50 g / m³). 2 The barrier layer, composed of a PET film, is obtained by appropriately adjusting the porous fiber layer to have a radiation frequency higher than 3 kHz and an average sound absorption value higher than 0.4. Furthermore, this mass layer according to the invention can be combined with a spring layer made of PET short fibers to obtain a sound-attenuating decorative part according to the invention that is excellent in terms of recyclability (made of 100% PET) and lightweight.

[0084] These two examples represent only two of the many possibilities for combining the porous fiber layer, barrier layer, and spring layer according to the preferred embodiments previously described in this invention. Other combinations can be envisioned by those skilled in the art, depending on the specific circumstances.

[0085] Furthermore, to improve the acoustic performance of the sound-attenuating decorative component according to the invention, a thin porous fiber layer (commonly referred to in the art as a "scrim") or a microperforated polymer foil with a tuned airflow resistance (AFR) can be laminated at least on a portion of the side surface of the porous fiber layer, which faces the porous fiber layer along its side adjacent to the barrier layer. To achieve the desired improvement in the acoustic performance of the sound-attenuating decorative component according to the invention, in all areas where the fiber scrim or microperforated membrane is applied, the AFR of the fiber scrim or microperforated polymer foil is preferably higher than that of the porous fiber layer, more preferably at least 20% higher. The areal weight of the fiber scrim or microperforated polymer foil is preferably not higher than 400 g / m². 2 More preferably not higher than 200g / m 2 So as not to significantly increase the total weight of the sound attenuation decorative component according to the invention.

[0086] Preferably, the additional fiber lining or microporous foil is made of one or more materials belonging to the same chemical class as the materials constituting the porous fiber structure layer, so as to facilitate recycling.

[0087] To further enhance the acoustic performance within the vehicle, the sound-attenuating trim component according to the invention may further include one or more additional acoustic absorbers located on the side of the porous fiber layer opposite to the side adjacent to the barrier layer. The additional acoustic absorbers may comprise any type of sound-absorbing material known in the art, such as fibrous materials like nonwoven textiles or felt, or porous materials like open-cell foam, particularly polyurethane foam. The additional acoustic absorbers may be in the form of a layer comprising one or more sound-absorbing materials. In this case, such additional acoustic absorbers may be laminated together with the porous fiber layer, and the acoustic absorbers may be structurally attached to the porous fiber layer by gluing and / or nailing and / or welding (e.g., ultrasonic welding). Such additional acoustic absorbers may completely or partially cover the surface of the porous fiber layer. Preferably, the additional acoustic absorbers are made of one or more materials belonging to the same chemical class as the materials constituting the porous fiber layer, to facilitate recycling.

[0088] All the aforementioned means of enhancing the in-vehicle acoustics of the sound-attenuating decorative component according to the invention, namely, adding a lining mesh and / or micro-perforated foil and / or additional absorbers, can be combined where technically possible and known in the art. For example, the micro-perforated polymer foil can be laminated onto at least a portion of the porous fiber layer along the side opposite to the side adjacent to the barrier layer, and furthermore, a layer of sound-absorbing material can be added on top of the micro-perforated foil.

[0089] The sound attenuation decorative component according to the present invention can be manufactured using production processes known in the art.

[0090] The first production process, applicable to cases where the spring layer is a fiber layer, includes at least the following steps:

[0091] (a1) A first fiber nonwoven layer, a barrier layer, and a second fiber nonwoven layer are stacked on top of each other, wherein the first fiber nonwoven layer is above the barrier layer and the barrier layer is above the second fiber nonwoven layer.

[0092] (b1) The multilayer thus obtained is placed on the lower half of the molding tool. The molding tool includes a lower half and an upper half, which, when closed, define a cavity having the three-dimensional shape required for the sound-attenuating decorative part according to the invention;

[0093] (c1) The molding tool is closed, and hot steam is injected into the mold cavity from the upper mold half and the lower mold half at approximately the same pressure, increasing the pressure from 0 bar to a maximum pressure, preferably between approximately 5 bar and 6 bar. For this step to be performed, both the upper and lower mold halves must be equipped with channels for injecting steam into the mold cavity;

[0094] (d1) After a time interval sufficient for the hot steam to solidify the fiber layers and allow them to adhere to the barrier layer, the steam is discharged through the upper half of the molding tool and through the lower half. For this venting operation, the same channel used in step (c1) to inject steam into the molding tool cavity can be used;

[0095] (e1) Apply a vacuum from the upper half of the mold to press the first porous fiber layer against the upper half of the mold;

[0096] (f1) Open the molding tool and remove the molded part from it.

[0097] Additional steps may include cutting (e.g. in a shearing tool) and cooling (e.g. in a cooling jig equipped with a cooling fan) the molded part.

[0098] In step (e1) of the first production process described above, the first fiber nonwoven fabric is pressed against the upper mold half, so that it, together with the barrier layer, possesses the properties required to achieve the quality layer of the present invention. In step (c1), both fiber layers are cured due to the action of hot steam, and also due to the hot steam, they adhere to the barrier layer. To promote this adhesion, the sides of the barrier layer are preferably treated with an adhesion primer before stacking the layers in step (a1).

[0099] In the second production process, which is a variant of the first production process described above, step (e1) is replaced by step (e2), in which hot steam is injected from the lower mold half to compress the first fiber layer between the upper mold half and the barrier layer.

[0100] With this variation, a higher pressure can be obtained to compress the first porous fiber layer compared to the case of the first production process, which may be useful, for example, when the first porous fiber layer has a high areal weight.

[0101] In the third production process, which is also a variation of the first production process, step (e1) is skipped and step (c1) is replaced by step (c3). Hot steam is injected from both the upper and lower mold halves. In the first stage, the hot steam pressure increases from 0 bar to a maximum value, preferably in the range of 5 to 6 bar. In the second stage, the pressure remains constant at this maximum value. During the pressure increase stage, the pressure of the hot steam injected from the lower mold halves is higher than that of the hot steam injected from the upper mold halves, preferably by an amount between 1 and 2 bar. In this way, the first porous fiber layer between the barrier layer and the upper mold halves is compressed, while the fiber layers are cured and adhered to the barrier layer.

[0102] This variation reduces the number of process steps compared to the first and second production processes described above, and makes the process less energy-intensive.

[0103] The fourth production process, which can be applied when the spring layer is a foam layer, includes at least the following steps:

[0104] (a4) Stack the first fiber nonwoven layer and the barrier layer on top of the other;

[0105] (b4) The multilayer thus obtained is placed on the lower half of the first molding tool. The first molding tool consists of a lower half and an upper half, which, when closed, define a first mold cavity having the three-dimensional shape required for the mass layer according to the invention. Furthermore, both the lower and upper half are maintained at a temperature sufficient to cure the first fiber nonwoven and allow it to adhere to the barrier layer, preferably between 160°C and 200°C, and even more preferably between 160°C and 180°C.

[0106] (c4) Close the first molding tool and keep it closed for a period of time sufficient to cure the first fiber nonwoven and allow it to adhere to the barrier layer. In this step, the first fiber nonwoven is also compressed in the first molding tool to achieve the properties required to achieve the quality layer according to the invention, together with the barrier layer.

[0107] (d4) Open the molding tool and remove the molded quality layer according to the invention from it;

[0108] (d5) The molded mass layer according to the invention is placed on the lower half of a second molding tool, which is a foaming tool, i.e., a tool that can inject polyurethane foam precursor into the mold cavity through an injection head present in the upper half of the mold. The second molding tool includes a lower half and an upper half, which, when the first molding tool is closed, define a second mold cavity having the three-dimensional shape required for the sound-attenuating decorative component according to the invention;

[0109] (d6) Close the second molding tool and inject the polyurethane foam precursor into the mold cavity;

[0110] (d7) After a time interval sufficient for the foam precursor to react, fill the unoccupied volume of the mold cavity with polyurethane foam and adhere to the barrier layer, open the second molding tool.

[0111] (d8) Remove the molded part from the mold.

[0112] In this fourth production process, the production of the sound-attenuating decorative component according to the invention is divided into two general steps: producing the mass layer according to the invention by means of thermoforming, and adding the spring layer. In the above list of steps, the case where the spring layer is a foam layer is considered. However, a significant variation is conceivable, applying a similar process to the case of a fiber spring layer, wherein in the second general step, the spring layer is simply overmolded onto the top of the mass layer.

[0113] The four production processes described above for manufacturing the sound-attenuating decorative parts according to the present invention are merely examples. Those skilled in the art can conceive of further production processes, such as those based on cold forming.

[0114] Furthermore, all embodiments previously described for the sound-attenuating decorative component according to the invention represent only possible material arrangements for obtaining such a sound-attenuating component. By considering the characteristics of the materials described herein, particularly their properties, density, thickness, and areal weight, those skilled in the art can derive other material arrangements that may be suitable depending on the circumstances from these embodiments.

[0115] In addition, other embodiments of the sound attenuation decorative component according to the invention can be derived from the description by combining different embodiments and examples of the invention, or from the description of the embodiments shown in the accompanying drawings. The drawings are schematic and not necessarily to scale. All disclosed scopes include end points. Attached Figure Description

[0116] Figure 1a A sound attenuation decorative component belonging to the prior art is shown, and Figure 1b A cross-section of this type of component is shown.

[0117] Figure 2a A sound attenuation decorative component according to the present invention is shown, and Figure 2b A cross-section of this type of component is shown.

[0118] Figure 3 A comparison is shown between the acoustic effect of the sound attenuation decorative component according to the present invention and the acoustic effect of a sound attenuation decorative component belonging to the prior art. Detailed Implementation

[0119] Figure 1a An example of a typical sound-attenuating decorative component 10 belonging to the prior art is shown, namely an interior partition of a dashboard, wherein there is a sound-insulating region 11 with primary sound insulation performance and a sound-absorbing region 12 with primary sound absorption performance. Figure 1a In the sound attenuation decorative component shown, the sound-absorbing region 12 covers the upper portion of the sound attenuation decorative component 10, corresponding to approximately 60% of its total surface area, while the sound-insulating region 11 covers the lower portion of the sound attenuation decorative component 10, corresponding to approximately 40% of its total surface area.

[0120] Figure 1b It shows Figure 1a A representative cross-section A-A' of the sound-attenuating decorative component 10 is shown. The sound-attenuating decorative component 10 includes a spring layer 13, a barrier layer 14, and porous fiber layers (15, 16). The porous fiber layers (15, 16) have variable thicknesses. In the lower portion 16 corresponding to the sound-insulating region 11, it has a substantially constant thickness of approximately 3.8 mm, while in the upper portion 15 corresponding to the sound-absorbing region 12, it has a substantially constant thickness of approximately 7.0 mm. According to the teachings of the prior art, higher compression of the porous fiber layer 16 is required in the sound-insulating region to impart mass spring characteristics to that region, thus achieving good sound insulation performance; however, this is very detrimental to sound absorption in the same region. Similarly, a higher height (i.e., lower compression) of the porous fiber layer 15 is required in the sound-absorbing region to impart higher sound absorption performance to that region; however, this is very detrimental to sound insulation in the same region.

[0121] In the sound-attenuating decorative component 10, which belongs to the prior art, the porous fiber layers (15, 16) are formed by heat compression, with an area weight of approximately 1000 g / m². 2 The semi-finished product is obtained by air-forming a web, which consists of approximately 75% recycled cotton fibers and 25% PET / CoPET core-sheath adhesive short fibers. In the same section, the barrier layer 14 consists of a thick layer of EVA with a density of approximately 3.5 kg / m³. 2 The spring layer 13 has a constant area weight and a constant thickness of approximately 1.9 mm. It is obtained by forming a semi-finished fiber web using compressed airflow, and the fiber web has an area weight of approximately 1000 g / m².2 It is composed of approximately 80% recycled cotton fibers and 20% PET / CoPET core-sheath adhesive short fibers. Therefore, the total area weight of this sound-attenuating decorative component 10 is approximately 5500 g / m². 2 .

[0122] The compressive dynamic Young's modulus of the porous fiber layers (15, 16) was measured, and the results were 413.5 kPa in the sound insulation region 11 corresponding to a thickness of 3.8 mm for the porous fiber layer 16, and approximately 120 kPa in the sound absorption region 12 corresponding to a thickness of 7.0 mm for the porous fiber membrane 15. From these values, it can be deduced that the radiation frequency corresponding to the mass layer in the sound insulation region 11 is approximately 3550 Hz, while the radiation frequency of the mass layer in the sound absorption region 12 is approximately 1910 Hz, and thus much lower than 3 kHz. According to the teachings of the prior art, this strong reduction in radiation frequency clearly indicates that the sound insulation in the sound absorption region 12 is significantly lower than that in the sound insulation region 11, especially in the frequency range around 2 kHz, which is a frequency range highly relevant to interior noise in vehicle acoustics.

[0123] The average sound absorption of the mass layer was also measured, again for the porous fiber layers (15, 16) at two thickness values ​​of 3.8 mm and 7.0 mm, corresponding to the sound insulation region 11 and the sound absorption region 12, respectively. The average sound absorption of the mass layer in the sound insulation region 11 was 0.255, while the average sound absorption of the sound absorption region was 0.437. This indicates that, consistent with the teachings of the prior art, compressing the porous fiber layer in the sound insulation region 11 is very detrimental to the sound absorption of that region.

[0124] Figure 2a A sound attenuation trim component 20 according to the present invention is shown. This is an interior partition for the dashboard, and its overall shape is similar to... Figure 1a The two areas are the same, but there is no difference between the sound insulation area and the sound absorption area.

[0125] Figure 2b It shows Figure 2a The image shows a representative cross-section A-A' of the sound-attenuating decorative component 20. This sound-attenuating decorative component 20 includes a spring layer 21, a barrier layer 22, and a porous fiber layer 23. The porous fiber layer 23 has a substantially constant thickness of approximately 5.0 mm. In the sound-attenuating decorative component 20 according to the invention, the porous fiber layer 23 is compressed by heat to an area weight of approximately 1500 g / m². 2 The semi-finished product is obtained by air-forming a web-like process, which consists of approximately 80% recycled cotton fibers and 20% short fibers of PET / CoPET core-sheath adhesive. In this case, the semi-finished product used for the porous fiber layer 23 is needle-punched from both sides, with a total needle density of approximately 55 needles / cm². 2Still in the sound attenuation decorative component 20 according to the present invention, the barrier layer 22 is composed of a thick layer of EVA, with an area weight of approximately 3000 g / m². 2 The thickness is approximately 1.6 mm, and the spring layer 21 is the same as the spring layer of the sound-attenuating interior trim component 10, which belongs to the prior art. The total area weight of the sound-attenuating trim component 20 according to the invention is approximately 5500 g / m². 2 Therefore, it has the same area and weight as the sound attenuation decorative component 10, which belongs to the prior art.

[0126] The dynamic Young's modulus of compression of the porous fiber layer 23 was measured, and the result was approximately 832 kPa. This value was obtained by averaging the results of five samples. For each sample, the test was conducted under a load of 1181 g, and the average value was taken in the frequency range of 300 Hz to 700 Hz. Based on the above value of the dynamic Young's modulus of compression, the radiation frequency of the mass layer of the sound attenuation decorative component 20 can be deduced to be approximately 5 kHz, which is much higher than 3 kHz.

[0127] The average sound absorption of the mass layer (22, 23) was measured and the result was equal to 0.40.

[0128] The acoustic effect of the sound attenuation decorative component 20 according to the present invention was compared with the acoustic effect of the sound attenuation decorative component 10 belonging to the prior art. The acoustic effect or noise reduction was calculated according to the procedure described, for example, in Section 6.4 of Pierce, A., D.'s "Acoustics - An introduction to its Physical Principles and Applications," McGraw-Hill Book Company, 1981. According to this procedure, the acoustic effect or noise reduction of the sound attenuation decorative component can be calculated by the following formula:

[0129] Where TL is the diffusion field transport loss of the decorative component, and ABS is the diffusion field absorption area of ​​the decorative component, in m². 2 And S is the surface area of ​​the same component, also in meters. 2 .for Figure 1a and Figure 2a The sound attenuation decorative component shown has an area of ​​1.33m². 2 As is known in the art, the diffusion field transmission loss corresponds to the dB value of the transmission coefficient, with the opposite sign.

[0130] The TL and ABS of the sound attenuation decorative component 20 according to the present invention are achieved by means of having with Figure 2aand Figure 2b The results were obtained by testing flat multilayers of the same layered components shown. Both tests involved the materials used and the associated area weight and thickness. TL was measured in the commercially available Isokell measurement system. ABS was measured in the commercially available Alpha Cabin measurement system. These two measurement systems are described in Chappuis, A., “Small Size Devices for Accurate Acoustical Measurements of Materials and Parts Used in Automobiles,” SAE Technical Paper 931266, 1993.

[0131] Similar tests were conducted to measure the transmission coefficient (TL) and absorption coefficient (ABS) of the sound-insulating region 11 and sound-absorbing region 12 of the sound-attenuating decorative component 10, which belongs to the prior art. The TL of the sound-attenuating decorative component 10 was obtained by weighted averaging of the transmission coefficients of the two different regions 11 and 12, with the weight of each region equal to the corresponding coverage (0.4 for the sound-insulating region and 0.6 for the sound-absorbing region in the case of the sound-attenuating decorative component 10). Based on the ABS values ​​of the sound-insulating region 11 and the sound-absorbing region 12, the ABS of the sound-attenuating decorative component 10 was calculated following a similar procedure.

[0132] Figure 3 The acoustic effect or noise reduction of the sound attenuation decorative component 20 according to the present invention is shown in solid lines. In the same... Figure 3 In the figure, the acoustic effect or noise reduction of the sound-attenuating decorative component 10, which belongs to the prior art, is shown by dashed lines. It can be seen from this figure that the overall improvement achieved by the sound-absorbing decorative component 20 according to the invention is clear, covering a very wide frequency range, particularly most of the frequency range between 800 Hz and 6300 Hz.

Claims

1. A noise attenuating trim part comprising at least one region having mass-spring properties, the at least one region comprising a spring layer and a mass layer, wherein, Said mass layer consists of a barrier layer and a porous fibrous layer adjacent to each other and laminated with said barrier layer between said spring layer and said porous fibrous layer, characterized in that said mass layer has a radiation frequency of at least 3 kHz and said porous fibrous layer has an average sound absorption of at least 0.

40.

2. The sound attenuating trim component of Claim 1, wherein, Said at least one area covers at least 50%, preferably at least 65%, even more preferably at least 80% of the surface of said noise attenuating trim part.

3. The sound attenuating trim component of claim 1 or 2, wherein, The thickness of said mass layer is substantially constant.

4. The sound attenuating trim part of any of the preceding claims, wherein, The porous fibrous layer is an air-laid needled porous fibrous layer, preferably with a needling density of at least 35 needles / cm 2 , more preferably at least 40 needles / cm 2 , even more preferably at least 50 needles / cm 2 .

5. The sound attenuating trim part of any of the preceding claims, wherein, The thickness of said porous fibrous layer is between 2 mm and 10 mm, preferably between 3 mm and 8 mm, even more preferably between 4 mm and 7 mm.

6. The sound attenuating trim part of any of the preceding claims, wherein, The area weight of said porous fibrous layer is between 500 gsm and 2000 gsm, preferably between 800 gsm and 1800 gsm, even more preferably between 1000 gsm and 1500 gsm.

7. The sound attenuating trim part of any of the preceding claims, wherein, The barrier layer has an area weight between 10 g / m 2 and 200 g / m 2 , preferably between 50 g / m 2 and 150 g / m 2 .

8. The sound attenuating trim part of any of the preceding claims, wherein, The barrier layer has an area weight between 500 g / m 2 and 8000 g / m 2 , preferably between 1500 g / m 2 and 5000 g / m 2 , even more preferably between 2000 g / m 2 and 3500 g / m 2 .

9. The sound attenuating trim part of any of the preceding claims, wherein, The radiation frequency of said mass layer is at least 5000 Hz, preferably at least 6300 Hz.

10. The sound attenuating trim part of any of the preceding claims, wherein, Said porous fibrous layer comprises natural regenerated fibers, preferably cotton regenerated fibers, and a binder, preferably a thermoplastic binder, even more preferably a thermoplastic binder consisting of bicomponent thermoplastic fibers.

11. The sound attenuating trim component of any one of claims 1 to 9, wherein, Said porous fibrous layer comprises thermoplastic bicomponent filaments consisting of a first polymer having a higher melting temperature and a second polymer having a lower melting temperature, preferably thermoplastic bicomponent filaments consisting of terephthalate-based polyesters.

12. The sound attenuating trim component of any one of claims 1 to 9, wherein, Said porous fibrous layer comprises fibers consisting of terephthalate-based polyesters and a thermoplastic binder, said thermoplastic binder preferably being a thermoplastic binder consisting of polypropylene (PP) fibers.

13. The sound attenuating trim part according to any one of claims 1 to 9, wherein said spring layer, said barrier layer and said porous fibrous layer comprise materials belonging to the same chemical class, preferably comprising materials belonging to the terephthalate-based polyesters class.

14. A method for producing a sound attenuating trim part according to claim 1, comprising at least the following steps: (a) a first fibrous nonwoven layer, a barrier layer and a second fibrous nonwoven layer are stacked one on top of the other, with said first fibrous nonwoven layer above said barrier layer and said barrier layer above said second fibrous nonwoven layer; (b) the multilayer thus obtained is placed on the lower half-mold of a molding tool comprising an upper half-mold and a lower half-mold which, when closed, define a cavity having the desired shape for said noise attenuating trim part; (c) the multilayer is molded by closing the upper half-mold and the lower half-mold of the molding tool, thus obtaining a molded multilayer; and (d) the molded multilayer is removed from the molding tool. (c) injecting hot steam into the molding tool cavity from both the upper half mold and from the lower half mold in order to cure the fibrous layer and adhere it to the barrier layer, wherein the pressure of the hot steam injected from the lower half mold and from the upper half mold is first increased from 0 bar to a maximum value preferably comprised between 5 and 6 bars, then kept constant at this maximum value, and wherein, during the pressure increase phase of the hot steam pressure, the pressure of the hot steam injected from the lower half mold is higher than the pressure of the steam injected from the upper half mold, preferably by an amount comprised between 1 and 2 bars, so as to compress the first porous fibrous layer between the barrier layer and the upper half mold; (d) after a time interval during which the hot steam is sufficient to cure the fibrous layer and adhere it to the barrier layer, steam is evacuated through both the upper half mold and the lower half mold of the molding tool; (e) opening the molding tool and removing the molded part therefrom.

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