Sound absorption and sound insulation noise reduction trim parts for automobiles

Abstract

The present invention relates to a sound-dampening trim component for automobiles that features both sound insulation and sound absorption properties. The trim component has mass spring characteristics and therefore comprises a spring layer and a mass layer. The mass layer consists of a barrier layer and a porous fiber layer that are adjacent to each other and laminated together, with the barrier layer located between the spring layer and the porous fiber layer, and the mass layer has a radiation frequency of at least 3 kHz and an average sound absorption value of at least 0.40.

Description

[Technical Field]

[0001] The present 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] Road vehicles have several noise sources that can emit noise across a very wide frequency range, typically from at least 100 Hz to 10 kHz. Because this frequency range covers a large portion of the audible frequency range, this can cause discomfort to occupants.

[0003] Noise-reducing trim components for improving the acoustic comfort of occupants in road vehicles are well known in the art. These components can be mounted on the body panels so as to cover at least a portion of the surface of the body panel. An example of such noise-reducing trim components is a dash inner insulator, which is generally mounted on the firewall of the body and substantially covers its entire surface. In other cases, noise-reducing trim components may not be mounted on the body panels but rather directly on the noise source and cover at least a portion of it. An example of such noise-reducing trim components is an engine top cover, which is typically mounted directly on the vehicle engine and covers its upper area.

[0004] Both of the examples above concern components whose primary purpose is to reduce noise radiated by the powertrain. However, in road vehicles, several noise-reducing trim components are commonly found that address other sources of noise. Examples include carpet insulators and wheel well inner insulators, whose primary purpose is to reduce noise radiated from the tires.

[0005] The noise attenuation trim part can fulfill its function by its sound absorption performance and / or sound insulation performance. Sound insulation refers to the ability of the noise attenuation trim part to reflect and return the acoustic energy carried by the sound wave that collides with it. Sound absorption refers to the ability of the noise attenuation trim part to dissipate internally the acoustic energy carried by the sound wave that collides with it.

[0006] When installed in a road vehicle, both sound absorption and sound insulation contribute to the acoustic effect of the noise attenuation trim part. Therefore, it is desirable for the noise attenuation trim part to have both sound insulation performance and sound absorption performance. However, the contribution of sound insulation and / or sound absorption to the acoustic effect of the noise attenuation trim part may depend on the frequency.

[0007] Typically, the contribution of sound insulation of the noise attenuation trim part to the in-vehicle acoustic effect is only important in the frequency range up to about 3 kHz, particularly in the frequency range of 800 Hz to 3 kHz. Above 3 kHz, there may be a side path propagation path that may not be blocked by the noise attenuation trim part installed either on the vehicle body panel and / or around the noise source, and may contribute in a relevant form to the transmission of noise into the passenger compartment of the road vehicle. On the other hand, the contribution of sound absorption of the noise attenuation trim part to the acoustic effect is generally only important above about 800 Hz. Since the thickness of the noise attenuation trim part is generally limited by packaging constraints, the sound absorption of the noise attenuation trim part for frequencies below 800 Hz is generally small. The frequency range of 800 Hz to 3 kHz is a frequency range in which both sound insulation and sound absorption can be important for the effectiveness of the noise attenuation trim part when the noise attenuation trim part is installed in a vehicle.

[0008] An example of a noise attenuation trim part having both sound insulation performance and sound absorption performance is disclosed in European Patent No. 2684187. In particular, this document discloses a noise attenuation trim part provided with a sound insulation region and a sound absorption region. The sound insulation region has good sound insulation performance. On the other hand, the sound absorption region has good sound absorption performance.

[0009] More specifically, according to the disclosure of European Patent No. 2684187, the sound-insulating region has acoustic mass spring properties and comprises a decoupling layer and a mass layer, the mass layer being realized by 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:

number

[0010] While it is true that noise-reducing trim components, such as those disclosed in European Patent No. 2684187, can combine sound insulation and sound absorption properties, the methods used to achieve this combination are not optimal, and several practical problems have been raised.

[0011] Firstly, in such a component, the sound-insulating region has poor or no sound-absorbing performance because, in the sound-insulating region, the porous fiber layer must be strongly compressed to achieve the desired compressive dynamic Young's modulus. At the same time, in such a component, the sound-absorbing region has poor or no sound-insulating performance because, in the sound-absorbing region, the porous fiber layer must be thickened to achieve the desired absorption performance, and therefore may not function as a mass layer even when combined with the backing barrier layer. As a result, the noise-reducing trim component according to European Patent No. 2684187 has a separation between the sound-blocking region and the sound-absorbing region, with the sound-blocking region having poor or no sound-absorbing performance and the sound-absorbing region having poor or no sound-insulating performance. This fact inevitably limits the acoustic effect of the component when installed in a vehicle.

[0012] In addition, the realization of the noise-reducing trim component described in European Patent No. 2684187 may require a porous fiber layer with variable thickness, which complicates and increases the cost of the component's design, production method, and the necessary tooling. [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] Therefore, an object of the present invention is to provide solutions to these problems of the prior art. The present invention as described herein makes it possible to obtain a noise-reducing trim component that optimally combines sound insulation and sound absorption and can be designed and manufactured in a simple and cost-effective manner. [Means for solving the problem]

[0014] The object of the present invention is achieved by the noise-reducing trim component described in claim 1 and the manufacturing method described in claim 14.

[0015] In its main embodiment, the present invention relates to a sound-attenuating trim component having at least one region having mass-spring characteristics comprising a spring layer and a mass layer. In the sound-attenuating trim component according to the present invention, the mass layer consists of a barrier layer and a porous fiber layer that are adjacent to each other and laminated together, the barrier layer being located between the spring layer and the porous fiber layer. Furthermore, in the sound-attenuating trim component according to the present invention, the mass layer has a radiation frequency of at least 3 kHz and an average sound absorption value of at least 0.40.

[0016] Surprisingly, it has been found that the acoustic effect of the sound attenuation trim component according to the present invention is significantly improved compared to prior art solutions by comprising at least one region that provides both excellent sound insulation performance and excellent sound absorption performance. The excellent sound insulation performance of this region is obtained from its mass spring characteristics combined with a mass layer having a radiation frequency of at least 3 kHz. At the same time, its excellent sound absorption performance is obtained from having an average sound absorption value of at least 0.40. The component according to the present invention shows a significant advancement compared to prior art solutions where the sound absorption performance and the sound insulation performance are limited to separate regions of the component and are not combined in the same region of the component, which is a fact that limits the acoustic effect of these prior art solutions.

[0017] The "radiation frequency" of a mass layer consisting of a barrier layer and a porous fiber layer adjacent to each other and laminated together is a specific frequency that can be evaluated using the following formula:

Equation

[0018] At the radiation frequency, a mass layer consisting of a porous fiber layer and a barrier layer adjacent to each other and laminated together can radiate noise very efficiently, whereby the noise blocking of a sound attenuation trim component having mass spring characteristics and comprising such a mass layer can be impaired, particularly at the radiation frequency of the mass layer and in the frequency range around it.

[0019] In this specification, “layer” is an object consisting of one or more materials and contained between two adjacent but separated surfaces, where the distance between the surfaces is substantially less than the dimensions of the surfaces. The two surfaces are referred to as “sides” of the layer, and they are opposite each other. The distance between the two surfaces is referred to as the thickness of the layer, which may be variable. In particular, a “barrier layer” is an airtight or air-impermeable layer, i.e., a layer that does not allow air to enter or exit.

[0020] In the mass layer according to the present invention, the radiation frequency is advantageously above 3 kHz, where the degradation of the sound insulation performance of the noise-reducing trim component according to the present invention has a limited effect on its acoustic effect. In fact, above 3 kHz, the transmission of noise to the occupant compartment of a road vehicle is typically strongly affected by side-path propagation, which may not be blocked by the noise-reducing trim component installed either on the vehicle body panel and / or around the noise source, thereby limiting the relevance of sound insulation to the acoustic effect of the noise-reducing trim component when installed on a vehicle.

[0021] The compressive dynamic Young's modulus is intended to be measured in the direction of the thickness of the porous fiber layer, hereafter referred to as the "out-of-plane" direction. The out-of-plane compressive dynamic Young's modulus of a porous fiber layer can be measured using a commercially available "Elwis-S" system. It should be noted that the out-of-plane compressive dynamic Young's modulus of a porous fiber layer is frequency-independent. Therefore, the out-of-plane compressive dynamic Young's modulus of a porous fiber layer can be obtained with sufficient engineering accuracy by measuring it at any frequency. Preferably, the out-of-plane compressive dynamic Young's modulus of a porous fiber layer is obtained by averaging over a frequency range, for example, 300 Hz to 700 Hz, to compensate for the unavoidable small fluctuations in frequency due to the inaccuracy of the measurement method.

[0022] The compressive dynamic Young's modulus of a porous fiber layer can be measured by extracting one or more samples of the same porous fiber layer from one or more regions of a sound-attenuating trim component, provided that the component is reasonably flat. A standard test using the Elwis-S system is performed on a circular sample having a diameter of 100 mm. However, if it is not possible to extract a reasonably flat sample of such diameter from a sound-attenuating trim component, the test can be performed on a sample with a smaller diameter. Preferably, the sample diameter should be at least 60 mm.

[0023] In addition, the load mass used in the Elwis-S test should be such that it ensures the sample under test is properly loaded and uniformly excited across its entire surface. For performing the test with a standard circular sample having a diameter of 100 mm, it is preferable to use a load mass containing 800 to 1300 grams. To perform the test with circular samples having different diameters, the upper load mass should be rescaled based on the sample surface.

[0024] The average sound absorption of an absorbing layer or multilayer is the frequency-average value of its absorption coefficient in the range of 800 Hz to 6.3 kHz, where the absorption coefficient is measured according to ISO 10534-2:1998 and expressed in 1 / 3 octaves. This quantity has been found to be particularly suitable for defining the influence that the sound absorption performance of a trim component may have on its acoustic effect when the trim component is installed in an automobile. This may be related to the fact that the indicated frequency range is the frequency range in which the human ear is most sensitive, according to the A-weighted curve, which is conventionally used in acoustics to take into account the sensitivity of the human ear. In fact, it is within this frequency range that the A-weighted curve has levels above approximately -1 dB.

[0025] In particular, in the case of the mass layer according to the present invention, the average sound absorption value is advantageously at least 0.4, which ensures that the acoustic absorption of the sound-attenuating trim component according to the present invention can substantially contribute to the in-vehicle acoustic effect of the same component over the frequency range to which the human ear is most sensitive, which differs from what happens with noise-attenuating trim components of the prior art.

[0026] The average sound absorption of a mass layer can be measured by taking one or more samples of the same porous fiber layer from one or more areas of a sound-attenuating trim component, which is reasonably flat. Standard measurements of the average sound absorption are performed on samples having diameters of 60 mm and 29 mm. It is usually not a problem to find one or more areas on the sound-attenuating trim component from which samples of this size can be taken that are reasonably flat. The average sound absorption of a mass layer is measured from the side of the porous fiber layer.

[0027] As is evident from all of the above, the mass layer according to the present invention combines features that impart an optimal combination of sound insulation and sound absorption performance to at least one region of the sound-attenuating trim component according to the present invention, thereby substantially improving the in-vehicle acoustic effect of this same trim component compared to prior art solutions.

[0028] This is achieved thanks to at least one region having mass spring characteristics, comprising a spring layer and a mass layer, the mass layer comprising a barrier layer and a porous fiber layer adjacent to each other, the barrier layer being between the spring layer and the porous fiber layer, the mass layer having a radiation frequency of at least 3 kHz, and the porous fiber layer having an average sound absorption value of at least 0.40. To further improve the acoustic effect of the sound-damping trim part according to the present invention, preferably the at least one region covers at least 50%, more preferably at least 70%, and even more preferably at least 85% of the surface of the trim part according to the present invention. Increasing the coverage of the at least one region actually leads to an improvement in the in-vehicle acoustic effect of the sound-damping trim part according to the present invention.

[0029] The mass layer according to the present invention consists of a porous fiber layer and a barrier layer adjacent to each other. The porous fiber layer according to the present invention may be very lightweight and thin, which is advantageous because it helps to limit the weight of the trim part according to the present invention and the packaging space required therefor. Preferably, the porous fiber layer according to the present invention is 500 g / m 2 ~2000g / m 2 More preferably 800 g / m² 2 ~1800g / m 2 Furthermore, a more comfortable 1000g / m 2 ~1500g / m 2 It has a surface weight. In addition, the thickness of the porous fiber layer according to the present invention is preferably 2 mm to 10 mm, more preferably 3 mm to 8 mm, and even more preferably 4 mm to 7 mm.

[0030] Furthermore, the density of the porous fiber layer according to the present invention is preferably 100 kg / m³. 3 ~600kg / m 3 , comfortably 200 kg / m 3 ~400kg / m 3 More preferably 250 kg / m 3 ~350 kg / m 3 Therefore, the higher the density of the porous fiber layer according to the present invention, the higher its compressive dynamic Young's modulus and, consequently, its radiation frequency. Thus, a high-density porous fiber layer is desirable. However, increasing the density of the porous fiber layer, in addition to increasing the weight of the sound-attenuating trim component according to the present invention, would lead to a significant increase in the force required to compress the porous fiber layer, thus potentially making its production difficult.

[0031] The area weight and thickness of the porous fiber layer according to the present invention may vary across its surface, as long as this does not impair the essential characteristics of the mass layer according to the present invention. However, preferably, the porous fiber layer according to the present invention has substantially constant thickness and substantially constant area weight across its entire surface. This may be advantageous because a porous fiber layer having substantially constant area weight and thickness simplifies the design and production methods of the sound-attenuating trim parts according to the present invention and requires less expensive tooling. Here, “substantially constant” means that the thickness and / or area weight of the porous fiber layer may vary from place to place by an amount corresponding to typical manufacturing tolerances and not affecting the essential characteristics of the mass layer according to the present invention. For example, a porous fiber layer having a thickness that varies across its surface by only 10% or less from its average value, e.g., 5.0 mm + / - 0.5 mm, can be considered to have substantially constant thickness, because such a variation in thickness corresponds to typical manufacturing tolerances and has only a slight effect on both the radiation frequency of the mass layer according to the present invention and the average sound absorption value of the same porous fiber layer according to the present invention. Similarly, and for the same reasons, always, for example, less than 5% of its average value across its surface, for example, 1500 g / m². 2 + / - 75g / m² 2 A porous fiber layer having a varying area weight can be considered to have a substantially constant area weight.

[0032] The porous fiber layer may contain any type of natural and / or synthetic fiber common in the industry. Examples of natural fibers include cotton, wool, flax, hemp, bamboo, sisal, jute, and abaca fibers. Examples of synthetic fibers include polypropylene fibers, polyethylene fibers, polyester fibers, e.g., polyethylene terephthalate (PET) fibers, polylactic acid (PLA) fibers, and polyamide (PA) fibers, particularly polyamide 6 or polyamide 6.6 fibers. Synthetic fibers may be one-component or two-component fibers. One-component fibers are made from a single material, while two-component fibers are synthetic fibers made from two polymers with different chemical and / or physical structures that are tightly connected to each other along the fiber length. Two-component fibers may be produced using methods known in the art, for example, by melt spinning. The porous fiber layer may consist of only one type of fiber, or it may be a mixture of different types of fibers.

[0033] Advantageously, the fibers of the porous fiber layer according to the present invention may be at least partially recycled in order to reduce the environmental impact of the method for manufacturing sound-dampening trim parts according to the present invention, particularly with respect to material consumption. In particular, the fibers of the porous fiber layer may be at least partially in the form of natural fiber reclaimed fibers, e.g., cotton reclaimed fibers, or synthetic fiber reclaimed fibers, e.g., polyester reclaimed fibers. One type of fiber reclaimed fiber is defined as containing at least 51% by weight of recycled fibers of the relevant material. Thus, for example, cotton reclaimed fibers contain at least 51% by weight of recycled cotton fibers, and the remaining 49% by weight consists of fibers of different materials and / or virgin fibers. Preferably, the porous fiber layer according to the present 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 natural fiber reclaimed fibers and / or synthetic fiber reclaimed fibers.

[0034] Furthermore, the porous fiber layer according to the present invention preferably contains a binder in an amount of 10% to 50% by weight, and more preferably 20% to 40% by weight. The binder may be thermosetting or thermoplastic. In either case, some kind of heat treatment is required to activate the binder. In the method for producing sound-dampening trim parts according to the present invention, the fibers of the porous fiber layer can be firmly bonded to one another along their entire length by the binder, at the same time that the trim parts are formed into the desired shape. This type of bonding method ensures that the porous fiber layer stably and durablely maintains the desired shape at the end of the method. Thermosetting binders are preferred when improvements in mechanical properties and structural consistency are required. On the other hand, binders in the form of thermoplastic binder fibers are preferred when very complex three-dimensional shapes must be achieved.

[0035] Thermosetting binders are preferably in the form of epoxy resins, phenolic resins, or mixtures thereof. Thermoplastic binders are preferably in the form of thermoplastic binder fibers. These are fibers that contain at least one portion which melts as a result of heat treatment and forms droplets that bind all other fibers together at their intersections / contact points. The melting point of the binder fiber (or the portion of the binder fiber that melts) must be significantly lower than the melting points of all other fibers (and any portions of the binder fiber that may not melt). Binder fibers can be one-component or two-component fibers. Particularly preferred as thermoplastic binder fibers are thermoplastic two-component core-sheath binder fibers. Thermoplastic two-component core-sheath binder fibers are two-component 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 heat treatment as described above. Furthermore, in a two-component core sheath binder fiber, the first polymer is preferably polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), and the second polymer is preferably a copolymer of polyethylene terephthalate (coPET) or a copolymer of polybutylene terephthalate (coPBT).

[0036] The fibers constituting the porous fiber layer may be short fibers or long fibers. This also applies to thermoplastic binder fibers that may be included in the porous fiber layer according to the present invention. Short fibers, unlike long filaments, are fibers provided in discontinuous predetermined lengths. In particular, the short fibers included in the porous fiber layer preferably have lengths ranging from 32 mm to 76 mm.

[0037] The fineness of the fibers constituting the porous fiber layer is preferably 0.5 denier to 10 denier, more preferably 0.5 denier to 5 denier, and even more preferably 0.5 denier to 2 denier. Finer fibers relative to a given mass of the porous fiber material provide better sound absorption performance.

[0038] The production of the porous fiber layer according to the present invention is preferably carried out by first preparing a nonwoven fiber cloth consisting of fibers of a desired fiber composition in the form of a soft mat, which is hereinafter referred to as a "semi-finished product" or simply a "semi-finished product," and then compressing it under heat.

[0039] The production of the semi-finished product may be carried out according to any method well known in the art. Such a method may include, in particular, the steps of forming a fiber web consisting of randomly oriented unbonded fibers of a desired composition, and joining the same fiber web. In addition to these two steps, the production of the semi-finished product may also include other steps, such as carding and cross-wrapping, which may be considered to give a particular preferred orientation of the fibers forming the web.

[0040] The steps of a method for forming a fiber web consisting of randomly oriented unbonded fibers of a desired composition may be carried out by techniques well known in the art, such as air-laying, wet-laying, spun-laying, melt-blowing, and electrospinning. The main objective of this step is to obtain a mixture of randomly oriented unbonded fibers having the desired composition as homogeneous as possible.

[0041] The above-described process of joining the fiber web may also be carried out by bonding techniques well known in the art, such as thermal bonding, chemical bonding, mechanical bonding, or a combination thereof. An example of thermal bonding is hot caraging and / or ultrasonic bonding. An example of chemical bonding is resin / spray powder bonding and / or foam bonding. An example of mechanical bonding is needle punching and / or water flow entanglement. The main purpose of this process is to loosely bond the fibers of the fiber web in the semi-finished product to each other so as to give the semi-finished product itself only the uniformity necessary for handling the semi-finished product during the production method of sound-dampening trim parts according to the present invention, while maintaining the form of a soft mat in the semi-finished product. Thus, the partial loose bonding of the fibers in the semi-finished product is quite different from the complete and strong bonding of the fibers that occurs during the production method of sound-dampening trim parts as described above.

[0042] However, quite surprisingly, the bonding technique used to join the fiber webs within the semi-finished product can affect the characteristics of the porous fiber layer according to the present invention, and this has been found to result from the compression of such semi-finished products under heating.

[0043] Preferably, the joining process of the semi-finished product used in the production of the porous fiber layer according to the present invention includes at least one needle punching step. Surprisingly, it has been found that with needle-punched semi-finished products, it may be possible to achieve the desired compressive dynamic Young's modulus of the porous fiber layer by compressing the porous fiber layer to a lesser extent compared to when other joining techniques are used for joining the porous fiber webs of the semi-finished products. As a result, by using needle-punched semi-finished products in its production, the porous fiber layer according to the present invention can be more easily tuned so that the mass layer according to the present invention simultaneously has a radiation frequency of over 3 kHz and an average sound absorption value of at least 0.4. In fact, the higher the compressive dynamic Young's modulus of the porous fiber layer, the higher the radiation frequency of the mass layer according to the present invention, and at the same time, the greater the thickness of the porous fiber layer, the higher the absorption of the mass layer according to the present invention.

[0044] To further enhance the aforementioned advantageous effects, the stitch density of the needle-punched semi-finished product used in the production of the porous fiber layer according to the present invention is at least 35 strokes / cm 2 , more preferably at least 40 strokes / cm 2 More preferably, at least 50 strokes / cm 2 That is the case.

[0045] The needle punching method may be applied from only one side of the semi-finished product or from both sides. If the needle punching method is applied from both sides, the stitch density mentioned above is the total stitch density. Furthermore, the stitch density mentioned here may refer not only to the semi-finished product used to produce the porous fiber layer according to the present invention by compression under heat, but also to this same porous fiber layer. When the porous fiber layer according to the present invention is compressed into a desired shape, the semi-finished product may expand or contract slightly, but this expansion or contraction is in strokes / cm 2 This does not substantially change the stitch density represented by [formula]. Therefore, the stitch density can also be evaluated in the final porous fiber layer.

[0046] It is hereby considered that the joining process of the semi-finished products used in the production of the porous fiber layer according to the present invention preferably includes at least one needle punching step, but it is important to note that this is not strictly necessary for the implementation of the present invention. Other joining techniques, such as thermal bonding and / or chemical bonding, may be used for joining semi-finished products as is well known in the art.

[0047] In a first preferred embodiment of the porous fiber layer according to the present invention, the porous fiber layer is obtained by compressing an air-ray needle-punched semi-finished product, i.e., a semi-finished product in which the web-forming step is carried out by the air-ray method and the web-joining step is carried out by the needle-punching method, under heating. Preferably, the stitch density of the needle-punching method is at least 35 strokes / cm 2 , more preferably at least 40 strokes / cm 2 More preferably, at least 50 strokes / cm 2Preferably, in this first embodiment of the porous fiber layer, the semi-finished product, and therefore the porous fiber layer obtained therefrom, also consists of a mixture of recycled cotton fibers and thermoplastic two-component binder 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 two-component binder fibers is preferably 10% to 40% by weight, more preferably 15% to 30% by weight. The thermoplastic two-component binder fibers are preferably PET / CoPET fibers.

[0048] This first preferred embodiment is advantageous in at least two respects. First, because recycled cotton fibers are present in the fiber mix, it contains a high amount of recycled material, which reduces the CO2 footprint of the sound-damping trim components according to the present invention, particularly in terms of material consumption. Second, the semi-finished products are obtained in a particularly simple manner, which does not involve carding and / or cloth wrapping. This makes it easy and affordable to manufacture the semi-finished products using a relatively simple nonwoven fabric manufacturing line.

[0049] In a second preferred embodiment, the porous fiber layer according to the present invention essentially consists of a thermoplastic two-component filament comprising a first polymer having a higher melting point and a second polymer having a lower melting point. The filament preferably has a core-sheath configuration. However, other configurations known in the art, such as a “parallel” configuration or a “sea-island” configuration, are also possible. The filament, hereafter also called “long filament,” is a continuous fiber having an indeterminate length, i.e., not cut to a specific length like a short fiber. In this preferred embodiment, the porous fiber layer according to the present invention is preferably obtained by processing a semi-finished product consisting of spunlaids, carded materials, and cross-wrapped fiber webs, compressing it under heat, and then joining them by a needle punching method.

[0050] In a thermoplastic two-component filament, the second polymer has a lower melting point than the first polymer, and as a result, when the two-component filament is heated, the first and second polymers react differently. When the two-component filament is heated to a temperature above the softening or melting point of the second polymer (e.g., the sheath polymer in a sheath core configuration) and below the melting point of the first polymer (e.g., the core polymer in a sheath core configuration), the second polymer softens or melts, while the first polymer does not. The softening of the second polymer makes it tacky and allows it to bond to adjacent filaments. Simultaneously, the melting of the second polymer causes the formation of droplets that bond adjacent fibers at their intersections, while the first polymer remains intact, forming a network of robust, long filaments in the final porous fiber layer.

[0051] In this embodiment, the porous fiber layer according to the present invention has excellent mechanical properties derived from the synergistic effect between the endless nature of the filaments and the properties of the two components. On the one hand, the long filaments are spread across 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 long filaments, and these bonding points are uniformly distributed along the entire length of the filaments themselves. As a result, a network of long filaments that is spread across the entire surface of the porous fiber layer according to the present invention and is strongly bonded to one another is obtained. Such a network has excellent mechanical properties, particularly with respect to bending stiffness. The amount of the second polymer is preferably 10% to 50% by weight, more preferably 20% to 40% by weight, relative to the weight of the porous fiber structure layer, in order to improve the bonding between the filaments.

[0052] Due to its excellent mechanical properties, this second embodiment of the porous fiber layer is particularly suitable for applications where the sound-damping trim components according to the present invention may be subjected to high levels of mechanical stress or vibration, such as powertrain encapsulants, engine covers, trunk floors, and wheel well outer liners.

[0053] In this embodiment, the porous fiber layer according to the present invention has a flexural modulus of at least 70 MPa, preferably 70 MPa to 1300 MPa, preferably 100 MPa to 950 MPa, and preferably 150 MPa to 700 MPa, measured at 23 degrees Celsius and 50% relative humidity in accordance with ISO 178:2019, so as not to deform substantially under the influence of structural load.

[0054] In a particularly preferred embodiment of this design, the long filaments are made of terephthalate polyester. A porous fiber layer made essentially of terephthalate polyester is advantageous for recycling. In this design, the first polymer, i.e., the polymer with a higher melting point, is preferably polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), and the second polymer, i.e., the polymer with a lower melting point, is preferably a copolymer of polyethylene terephthalate (coPET) or polybutylene terephthalate (coPBT). In this design, at least a portion of the polyester can always be advantageously recycled. For example, the PET used as the first polymer may be obtained by melting consumer products such as PET bottle flakes, or PET packaging, or PET marine products such as fishing nets, and forming them into pellets that can be used in the spinning process. Using recycled polyester has the advantage of reducing the environmental impact, particularly its CO2 footprint, of the method of producing the water shield according to the present invention. In this embodiment, preferably at least 20%, more preferably at least 50%, and even more preferably at least 70% of the polyester used in the two-component fibers is recycled polyester, and this percentage is a weight percentage calculated with respect to the total weight of the porous fiber structure layer.

[0055] The diameter of the two-component length filaments, when they are made of polyester, is preferably 14 to 37 microns, more preferably 20 to 25 microns, in order to achieve the required strength.

[0056] In a third preferred embodiment, the porous fiber layer according to the present invention essentially consists of a fibrous mixture comprising 20% ​​to 50% by weight of single-component PET short fibers, 20% to 50% by weight of thermoplastic two-component PET / CoPET binder short fibers, and 20% to 40% by weight of hollow composite single-component PET fibers. In this preferred embodiment, the porous fiber layer according to the present invention is obtained by treating a semi-finished product consisting of an airlaid fiber web having the above-described fiber composition and bonded by thermal bonding (e.g., by hot calendering) under heat.

[0057] Similar to the second preferred embodiment of the porous fiber layer described above, this third preferred embodiment is also 100% PET, which is particularly advantageous in terms of recyclability. In addition, the presence of hollow composite fibers in the fiber mixture makes it particularly lightweight and improves its sound absorption performance.

[0058] As described above with respect to a second preferred embodiment of the porous fiber layer, the PET of different components of the fibrous mix may, advantageously, be of recycled nature.

[0059] The mass layer according to the present invention consists of a porous fiber layer and a barrier layer adjacent to each other. The barrier layer may consist of any one or more materials, as long as it fulfills its primary function of acting as an acoustic barrier.

[0060] The area weight and material of the barrier layer can be important features in the design of the sound-attenuating trim component according to the present invention. In fact, the area weight and material of the barrier layer can be advantageously adjusted by those skilled in the art to achieve a desired trade-off between the weight of the sound-attenuating trim component according to the present invention and its sound insulation performance. The greater the area weight of the barrier layer, the better the sound insulation performance of the sound-attenuating trim component according to the present invention, particularly in the frequency range of 800 Hz to 3 kHz. However, at the same time, this makes the same component heavier, which is disadvantageous to the fuel consumption and CO2 emissions of the vehicle in which the component is ultimately installed.

[0061] In particular, when lightweight sound-attenuating trim components are desired, the area weight of the barrier layer is preferably 10 g / m². 2 ~200g / m 2 Comfortable 50g / m 2 ~150g / m 2 That is the case.

[0062] In this case, a preferred embodiment of the barrier layer according to the present invention is a polymeric film comprising at least one polymer or copolymer selected from the group consisting of polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT); polyamides such as polyamide 6 or polyamide 66; polyolefins such as polypropylene (PP) and polyethylene (PE); thermoplastic elastomers such as thermoplastic polyolefin (TPO) and thermoplastic polyurethane (TPU) (TPE); elastomers such as EPDM-based elastomers, butadiene-based elastomers, or silicones; high-performance polymers such as polytetrafluoroethylene (PTFE), polyetherimide, polysulfone, polyethersulfone, and polyetheretherketone (PEEK); ethylene vinyl acetate (EVA); and biopolymers such as polylactic acid (PLA).

[0063] Preferably, one or more materials used in the film and the materials used in the porous fiber layer belong to the same chemical group to facilitate recycling.

[0064] The film may be single-layer, double-layer, or multi-layer. Using a double-layer or multi-layer film can further improve stability, elasticity, and / or robustness.

[0065] In this embodiment of the barrier layer according to the present invention, the film preferably has a tensile strength greater than 20 MPa and a tensile fracture strain greater than 100%. If the film is anisotropic, these values ​​refer to both the mechanical and transverse directions. The tensile fracture stress and tensile fracture strain are measured according to ISO 527-1:2019 and 527-3:2018. Furthermore, the thickness of the film is preferably 10 to 200 micrometers, and more preferably 50 to 150 micrometers.

[0066] On the other hand, if a sound-attenuating trim component with particularly improved sound insulation is desired, the area weight of the barrier layer is preferably 500 g / m². 2 ~8000g / m 2 , comfortable 1500g / m 2 ~5000g / m 2 Even more comfortably, 2000g / m 2 ~3500g / m 2 That is the case.

[0067] In this case, a preferred embodiment of the barrier layer according to the present invention is a layer comprising a matrix of thermoplastic elastomer material filled with a large amount of inorganic filler. Such a layer is commonly referred to in the art as a "layer," is airtight, and is therefore suitable for functioning as a barrier layer in the sound-attenuating trim component according to the present invention.

[0068] In this embodiment of the barrier layer according to the present invention, one or more materials included in the thermoplastic elastomer matrix are preferably selected from the group consisting of ethylene vinyl acetate copolymer (EVA); polyester such as ethylene propylene diene monomer (EPDM), 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 PA-66; thermoplastic polymide (TPI); thermoplastic polyolefin (TPO); thermoplastic polyurethane (TPU); polytetrafluoroethylene (PTFE); polyether ether ketone (PEEK); acrylonitrile butadiene styrene (ABS); and 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.

[0069] In this embodiment of the barrier layer according to the present invention, the thickness of the barrier layer is always preferably 0.2 mm to 5 mm, more preferably 0.8 mm to 3 mm.

[0070] The selection of the barrier layer, particularly its area weight and material, may depend on the desired trade-off between the sound insulation performance and total weight of the sound-attenuating trim component according to the present invention. Furthermore, the selection of the barrier layer, particularly its area weight and material, 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 to at least partially the same chemical group. This facilitates a method for laminating the porous fiber layer and the barrier layer together. In fact, for the sound-attenuating trim component according to the present invention to achieve the desired effect, it is essential that the barrier layer and the porous fiber layer are adjacent to each other and that they are laminated together. Here, "laminated together" means that the barrier layer and the porous fiber layer are permanently combined so that they function together as a mass layer under the action of sound waves impacting the sound-attenuating trim component according to the present invention. The lamination method may be carried out by means such as heat and / or pressure and / or welding and / or adhesive.

[0071] In addition to the aforementioned advantages of the lamination method, having one or more materials in the barrier layer and one or more materials in the porous fiber material layer belong to at least partially the same chemical group is also advantageous for the recyclability of the sound-attenuating trim component at the end of its lifespan according to the present invention.

[0072] In the sound-damping trim component according to the present invention, the spring layer has the function of isolating the mass layer from sound waves and / or vibrations of a noise source.

[0073] Preferably, the spring layer has a dynamic compressive Young's modulus of 300 kPa or less, more preferably 150 kPa or less, and even more preferably 80 kPa or less. Furthermore, the spring layer has a thickness preferably ranging from 1 mm to 80 mm, more preferably 3 mm to 50 mm, and even more preferably 5 mm to 40 mm. In general, the lower the dynamic compressive Young's modulus and the greater the thickness, the better performance can be provided, i.e., the spring layer better isolates the mass layer from sound waves and / or vibrations of noise sources. However, in practice, the thickness may be limited by design constraints such as packaging space or cost.

[0074] The dynamic compressive Young's modulus of the spring layer can be measured using the commercially available Elwis-S tool in the same manner as described above for the porous fiber layer according to the present invention. However, for the spring layer, a load mass of 150 to 400 grams is preferred for the Elwis-S test. This value of load mass is based on a standard circular sample with a diameter of 100 mm. For samples with different dimensions, the load mass needs to be rescaled as described above.

[0075] In the sound-damping trim component according to the present invention, the spring layer may contain any material as long as it satisfies the main functions described above. Preferably, the spring layer contains a porous material and / or a cellular material, which is advantageous from the viewpoint of weight reduction.

[0076] In a first preferred embodiment, the spring layer according to the present invention is made of a nonwoven fiber cloth. In this embodiment, the fiber material used for the spring layer is essentially the same as that used for the porous fiber layer according to the present invention. However, the spring layer preferably has a lower density than the porous fiber layer according to the present invention, i.e., preferably is bulkier and less compressible. This is because it can improve its isolation function from noise / vibration from noise sources. In this embodiment, the density of the spring layer is preferably 30 kg / m³ 3 ~300kg / m 3 More preferably 40 kg / m 3 ~200kg / m 3 Furthermore, a more comfortable 50 kg / m 3 ~150kg / m 3 That is the case.

[0077] This first preferred embodiment of the spring layer according to the present invention may offer advantages in terms of recyclability at the end of life of the sound-damping trim component according to the present invention, particularly when one or more materials of the spring layer belong to the same chemical group as one or more materials of the barrier layer and the porous fiber layer.

[0078] In a second preferred embodiment, the spring layer according to the present invention is made of an open-cell foam, preferably a polyurethane foam. In this embodiment, the density of the foam is preferably 30 kg / m³ 3 ~200kg / m 3 More preferably 40 kg / m 3 ~120 kg / m 3 Furthermore, a more comfortable 50 kg / m 3 ~90kg / m 3 This embodiment of the spring layer may be advantageous because foam, particularly polyurethane foam, provides excellent moldability and greater design flexibility. Therefore, this embodiment may be advantageous when the sound-absorbing trim component according to the present invention is attached to a body panel and / or a noise source having a particularly complex three-dimensional shape.

[0079] All of the above preferred embodiments of the porous fiber layer, barrier layer, and spring layer according to the present invention can be advantageously combined by those skilled in the art, depending on the desired trade-offs between in-vehicle acoustic effects, weight, legal complexity, and design constraints.

[0080] For example, the mass layer according to the present invention can be obtained by combining the above-described first preferred embodiment of a porous fiber layer (consisting of an air-ray needle-punched porous fiber layer containing recycled cotton fibers and binder short fibers) which is appropriately adjusted to have a radiation frequency above 3 kHz and an average sound absorption value of at least 0.4, with a barrier layer made of EPDM. Furthermore, this mass layer according to the present invention may be combined with a spring layer made of foam to obtain an embodiment of a sound-attenuating trim component according to the present invention that has excellent sound insulation performance and is suitable for installation on vehicle panels and / or noise sources having a complex three-dimensional shape.

[0081] Similarly, the mass layer according to the present invention comprises a porous fiber layer (consisting of thermoplastic bicomponent filaments, preferably PET thermoplastic bicomponent filaments) appropriately adjusted to have a radiation frequency above 3 kHz and an average sound absorption value above 0.4, as described in the second preferred embodiment, and a lightweight PET film, for example, 50 g / m². 2This can be obtained by combining it with a barrier layer made of PET film. Furthermore, this mass layer according to the present invention may be combined with a spring layer made of PET short fibers to obtain a sound-damping trim component according to the present invention that is excellent in terms of recyclability (made of 100% PET) and lightweight.

[0082] These two examples represent only two of the many possibilities for combining the aforementioned preferred embodiments of the porous fiber layer, barrier layer, and spring layer according to the present invention. Those skilled in the art can envision other combinations depending on the circumstances of the case.

[0083] Furthermore, to enhance the acoustic effect of the sound-attenuating trim component according to the present invention, a thin fibrous porous layer (commonly known in the art as "scrim") or a microporous polymer foil having a controlled airflow resistance (AFR) may be laminated on at least a portion of the surface of the porous fiber layer opposite to the surface of the porous fiber layer adjacent to the barrier layer. To obtain the desired improvement in the acoustic properties of the sound-attenuating trim component according to the present invention, the AFR of the fibrous scrim or microporous polymer foil is preferably higher than the AFR of the porous fiber layer, and more preferably at least 20% higher than the AFR of the porous fiber layer, in all areas to which the fibrous scrim or microporous film is applied. The fibrous scrim or microporous polymer foil is preferably 400 g / m² in order not to substantially increase the total weight of the sound-attenuating trim component according to the present invention. 2 More preferably 200g / m² 2 It has the following area-to-weight ratio.

[0084] Preferably, the additional fibrous scrim or microporous foil is made of one or more materials belonging to the same chemical group as one or more materials constituting the porous fibrous structure layer, which is advantageous for recycling.

[0085] To further enhance the acoustic effect inside the vehicle, the sound-dampening trim component according to the present invention may further comprise one or more additional sound-absorbing materials located on the surface of the porous fiber layer opposite to the surface adjacent to the barrier layer. The additional sound-absorbing materials may include any type of sound-absorbing material known in the art, such as fibrous materials such as nonwoven fabrics or felt, or cellular materials such as open-cell foams, particularly polyurethane foams. The additional sound-absorbing materials may be in the form of a layer comprising one or more sound-absorbing materials. In this case, such additional sound-absorbing materials may be laminated together with the porous fiber layer and may be structurally connected to the porous fiber layer by adhesive and / or stapling and / or welding (e.g., ultrasonic welding). Such additional sound-absorbing materials may completely or partially cover the surface of the porous fiber layer. Preferably, the additional sound-absorbing materials are made of one or more materials belonging to the same chemical group as one or more materials constituting the porous fiber layer, for the benefit of recycling.

[0086] All of the above-described means for enhancing the in-vehicle acoustic effect of the sound-dampening trim component according to the present invention, namely the addition of scrim and / or microporous foil and / or additional absorbent material, are technically feasible and can be combined as is well known in the art. For example, the microporous polymer foil may be laminated on at least a portion of the porous fiber layer on the side opposite to the side adjacent to the barrier layer, and furthermore, a layer of acoustic absorbing material may be added on top of the microporous foil.

[0087] The sound attenuation trim component according to the present invention can be manufactured using production methods well known in the art.

[0088] A first production method applicable when the spring layer is a fiber layer includes at least the following steps: (a1) Laminating the first nonwoven fiber layer, the barrier layer, and the second nonwoven fiber layer on top of each other such that the first nonwoven fiber layer is on top of the barrier layer and the barrier layer is on top of the second nonwoven fiber layer, (b1) The multilayer body thus obtained is placed in the lower mold of the molding tool. Here, the molding tool comprises a lower mold and an upper mold that define a mold cavity having a three-dimensional shape desirable for the sound-attenuating trim part according to the present invention when the molding tool is closed. (c1) Close the molding tool and inject hot steam into the mold cavity from both the upper and lower molds at approximately the same pressure, increasing from 0 bar to a maximum pressure, preferably about 5 to 6 bar. To carry out this step, both the upper and lower molds must be provided with channels for injecting steam into the mold cavity. (d1) After a sufficient time interval for the high-temperature steam to harden the fiber layer and bond the fiber layer to the barrier layer, the above is discharged through both the upper and lower molds of the molding tool. For this discharge operation, the same channels used to inject the steam into the molding tool cavity in step (c1) may be used. (e1) Applying a vacuum from the upper mold in order to compress the first porous fiber layer relative to the upper mold, (f1) Open the molding tool and remove the molded part from the molding tool. Additional steps may include cutting the molded parts (e.g., with a shear cutting tool) and cooling them (e.g., with a cooling jig equipped with a cooling fan).

[0089] In step (e1) of the first production method described above, the compression of the first nonwoven fiber fabric against the upper mold is such that it imparts to the first nonwoven fiber fabric the properties necessary to realize the mass layer according to the present invention together with the barrier layer. In step (c1), both fiber layers are cured by the action of high-temperature steam and adhere to the barrier layer by the action of high-temperature steam. To promote this adhesion, it is preferable to treat both sides of the barrier layer with an adhesive primer before laminating the layers in step (a1).

[0090] In the second production method, which is a variation of the first production method described above, process (e1) is replaced by process (e2). Here, high-temperature steam is injected from the lower mold to compress the first fiber layer between the upper mold and the barrier layer. In this modified form, it is possible to obtain a higher pressure for compressing the first porous fiber layer compared to the first production method, which may be useful, for example, when the first porous fiber layer has a high area weight.

[0091] Similarly, in the third production method, which is a variation of the first production method, process (e1) is omitted and process (c1) is replaced by process (c3). Here, high-temperature steam is injected from both the upper and lower molds. In the first stage, the high-temperature steam pressure is increased from 0 bar to a maximum value, preferably in the range of 5 bar to 6 bar. In the second stage, the pressure is kept constant at this maximum value. During the pressure increase stage, the pressure of the high-temperature steam injected from the lower mold is higher than the pressure of the high-temperature steam injected from the upper mold, preferably by 1 to 2 bar. This hardens the fiber layer and causes it to adhere to the barrier layer, while compressing the first porous fiber layer between the barrier layer and the upper mold. In this modified form, the number of steps in the method can be reduced, and the requirements for energy consumption by the method can be lowered compared to the first and second production methods described above.

[0092] A fourth production method applicable when the spring layer is a foam layer includes at least the following steps: (a4) Laminating the first nonwoven fiber layer and the barrier layer together, (b4) The multilayer obtained in this manner is placed in the lower mold of the first molding tool. Here, the first molding tool consists of a lower mold and an upper mold that define a first mold cavity having a desirable three-dimensional shape for the mass layer according to the present invention when the first molding tool is closed. Furthermore, both the lower mold and the upper mold are maintained at a temperature sufficient to cure the first nonwoven fiber cloth and cause the first nonwoven fiber cloth to adhere to the barrier layer, preferably in the range of 160°C to 200°C, and more preferably in the range of 160°C to 180°C. (c4) Close the first molding tool and keep it closed for a sufficient time interval to cure the first nonwoven fabric and allow it to adhere to the barrier layer. In this step, the first nonwoven fabric is also compressed within the first molding tool together with the barrier layer to acquire the properties necessary to realize the mass layer according to the present invention. (d4) Open the molding tool and remove the molded mass layer according to the present invention. (d5) The molded mass layer according to the present invention is placed in the lower mold of a second molding tool, which is a foam molding tool, i.e., a tool in which a polyurethane foam precursor can be injected into a mold cavity through an injection head present in the upper mold. The second molding tool comprises a lower mold and an upper mold that define a second mold cavity having a three-dimensional shape desirable for the sound-attenuating trim part according to the present invention when the first molding tool is closed. (d6) Close the second molding tool and inject the polyurethane foam precursor into the mold cavity. (d7) After a sufficient time interval to allow the foam precursor to react, fill the volume of the mold cavity not occupied by the mass layer with polyurethane foam, and adhere to the barrier layer, open the second molding tool. (d8) The process of removing the molded parts from the mold.

[0093] In this fourth production method, the production of the sound-damping trim component according to the present invention is divided into two macro-steps: the production of the mass layer according to the present invention by thermoforming and the addition of the spring layer. The above list of steps considers the case where the spring layer is a foam layer. However, obvious variations can be envisioned in which the same method is applied to the case of a fiber spring layer, in which the spring layer is simply overmolded on top of the mass layer in the second macro-step.

[0094] The four production methods for sound-dampening trim parts according to the present invention described above are merely examples. Those skilled in the art may envision further production methods, such as production methods based on cold forming.

[0095] Furthermore, all embodiments described above with respect to the sound-attenuating trim component according to the present invention merely represent possible material arrangements for obtaining this same sound-attenuating component. By considering the characteristics of the materials described herein, in particular their properties, density, thickness and area weight, those skilled in the art can derive from these embodiments further material arrangements that may be appropriate depending on the situation.

[0096] In addition, further embodiments of the sound-attenuating trim component according to the present invention may be derived from the description by combining different embodiments and examples of the present invention, and also from the description of the embodiments shown in the figures. The drawings are schematic and not necessarily to scale. All extents disclosed include endpoints. [Brief explanation of the drawing]

[0097] [Figure 1a] Figure 1b shows a cross-section of a sound attenuation trim component belonging to the prior art. [Figure 1b] Figure 1b shows a cross-section of a sound attenuation trim component belonging to the prior art.

[0098] [Figure 2a] Figure 2b shows a cross-sectional view of a sound attenuation trim component according to the present invention. [Figure 2b] Figure 2b shows a cross-sectional view of a sound attenuation trim component according to the present invention.

[0099] [Figure 3] This shows a comparison between the acoustic effect of the sound-attenuating trim component according to the present invention and the acoustic effect of a sound-attenuating trim component belonging to the prior art. [Modes for carrying out the invention]

[0100] Figure 1a shows an example of a typical sound-attenuating trim component 10 belonging to the prior art, namely a dash inner insulator having a sound-insulating region 11 that mainly has sound-insulating properties and a sound-absorbing region 12 that mainly has sound-absorbing properties. In the sound-attenuating trim component shown in Figure 1a, the sound-absorbing region 12 covers the upper part of the sound-attenuating trim component 10, which corresponds to about 60% of its total surface, and the sound-insulating region 11 covers the lower part of the sound-attenuating trim component 10, which corresponds to about 40% of its total surface.

[0101] Figure 1b shows a typical cross-section A-A' of the sound-attenuating trim component 10 shown in Figure 1a. The sound-attenuating trim component 10 comprises a spring layer 13, a barrier layer 14, and porous fiber layers (15, 16). The porous fiber layers (15, 16) have variable thickness. In the lower part 16 corresponding to the sound-insulating region 11, the porous fiber layers (15, 16) have a nearly constant thickness of approximately 3.8 mm, and in the upper part 15 corresponding to the sound-absorbing region 12, the porous fiber layers (15, 16) have a nearly constant thickness of approximately 7.0 mm. According to prior art teachings, higher compression of the porous fiber layer 16 in the sound-insulating region is required to give this region mass spring characteristics and therefore good sound-insulating performance. However, this is highly undesirable for the sound absorption of this same region. Similarly, higher bulkiness (i.e., lower compression) of the porous fiber layer 15 in the sound-absorbing region is required to give this region higher sound absorption performance. However, this is highly undesirable for sound insulation in this same area.

[0102] In the conventional sound-attenuating trim component 10, the porous fiber layer (15, 16) is approximately 1000 g / m². 2 It is obtained by compressing an air array semi-finished product, which has an area weight of approximately 75% recycled cotton fibers and 25% PET / CoPET core sheath binder short fibers, under heating. In this same part, the barrier layer 14 has an area weight of approximately 3.5 kg / m 2 It consists of EVA layers having a constant area weight and a constant thickness of approximately 1.9 mm. The spring layer 13 has a weight of approximately 1000 g / m 2It has an area weight and is obtained by compressing an air array semi-finished fiber web consisting of approximately 80% recycled cotton fibers and 20% PET / CoPET core sheet (sheat) binder short fibers. Therefore, the total area weight of the sound-damping trim part 10 is approximately 5500 g / m². 2 That is the case.

[0103] When the compressive dynamic Young's modulus of the porous fiber layers (15,16) was measured, it was 413.5 kPa for the 3.8 mm thick porous fiber layer 16 corresponding to the sound insulation region 11, and approximately 120 kPa for the 7.0 mm thick porous fiber layer 15 corresponding to the sound absorption region 12. From these values, it can be estimated that the radiation frequency corresponding to the mass layer in the sound insulation region 11 is approximately 3550 Hz, and the radiation frequency of the mass layer in the sound absorption region 12 is approximately 1910 Hz, and therefore considerably below 3 kHz. According to the teachings of the prior art, this significant decrease in radiation frequency clearly indicates that the sound insulation performance in the sound absorption region 12 is substantially lower than that in the sound insulation region 11, particularly in the frequency range around 2 kHz, which is a frequency range highly relevant to internal noise in vehicle acoustics.

[0104] Similarly, the average sound absorption values ​​of the mass layer were measured for two thicknesses of porous fiber layers (15,16) 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 value of the mass layer in the sound insulation region 11 was 0.255, and the average sound absorption value in the sound absorption region was 0.437. This is consistent with prior art teachings and indicates that compression of the porous fiber layer in the sound insulation region 11 is highly undesirable for sound absorption in this region.

[0105] Figure 2a shows the sound attenuation trim component 20 according to the present invention. This is a dash inner insulator having the same overall shape as the one shown in Figure 1a, but there is no distinction between the sound insulation area and the sound absorption area.

[0106] Figure 2b shows a typical cross-section A-A' of the sound-attenuating trim component 20 shown in Figure 2a. The sound-attenuating trim component 20 comprises 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 about 5.0 mm. In the sound-attenuating trim component 20 according to the present invention, the porous fiber layer 23 has a density of about 1500 g / m 2 It is obtained by compressing an air-ray needle processed semi-finished product, which has a surface weight and consists of approximately 80% recycled cotton fibers and 20% PET / CoPET core sheath binder short fibers, under heat. In this case, the semi-finished product used for the porous fiber layer 23 is approximately 55 strokes / cm 2 It is needle-processed from both sides with a total needle-stitch density of . In the sound-attenuating trim part 20 according to the present invention, the barrier layer 22 is always approximately 3000 g / m 2 The spring layer 21 is made of EVA layers having an area weight and a thickness of approximately 1.6 mm, and is the same as that of the conventional sound-damping trim part 10. The total area weight of the sound-damping trim part 20 according to the present invention is 5500 g / m². 2 Therefore, the total area weight is the same as that of the sound attenuation trim component 10 belonging to the prior art.

[0107] The compressive dynamic Young's modulus of the porous fiber layer 23 was measured to be approximately 832 kPa. This value was obtained by averaging the results obtained from five samples. For each sample, the test was conducted with a load mass of 1181 grams, and the average was taken over the frequency range of 300 Hz to 700 Hz. From the above value of the dynamic compressive Young's modulus, it can be estimated that the radiation frequency of the mass layer of the sound-attenuating trim component 20 is approximately 5 kHz, and therefore considerably above 3 kHz.

[0108] The average sound absorption of the mass layer (22,23) was measured, and a result equivalent to 0.40 was obtained.

[0109] The acoustic effect of the sound-attenuating trim component 20 according to the present invention was compared with the acoustic effect of the sound-attenuating trim component 10 belonging to the prior art. The acoustic effect or noise reduction was calculated, for example, according to the procedure described in Section 6.4 of Pierce, A., D., "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-attenuating trim component can be calculated by the following formula.

number

[0110] The TL and ABS of the sound-attenuating trim part 20 according to the present invention were obtained from tests on a flat multilayer having the same laminated structure as the part shown in Figures 2a and 2b, relating both the material used and the associated area weight and thickness. The TL was measured using a commercially available measurement system, Isokell. The ABS was measured using a commercially available measurement system, Alpha Cabin. Both 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.

[0111] Similar tests were conducted to measure the TL and ABS of the sound-insulating region 11 and sound-absorbing region 12 of the sound-attenuating trim component 10 belonging to the prior art. The TL of the sound-attenuating trim component 10 was obtained by the weighted average of the transmission coefficients of two different regions 11 and 12, with the weight assigned to each region being equal to the corresponding coverage ratio (0.4 for the sound-insulating region and 0.6 for the sound-absorbing region in the case of the sound-attenuating trim component 10). Following a similar procedure, the ABS of the sound-attenuating trim component 10 was calculated from the ABS values ​​of the sound-insulating region 11 and sound-absorbing region 12.

[0112] Figure 3 shows the acoustic effect or noise reduction of the sound-attenuating trim component 20 according to the present invention with a solid line. In the same Figure 3, the acoustic effect or noise reduction of the prior art sound-attenuating trim component 10 is shown with a dashed line. As can be seen from this figure, the overall improvement obtained with the sound-absorbing trim component 20 according to the present invention is clear, covering a very wide frequency range, especially most of the 800Hz to 6300Hz frequency range.

Claims

1. A noise-damping trim component comprising at least one region having mass spring characteristics, wherein the region comprises a spring layer and a mass layer, the mass layer comprising a barrier layer and a porous fiber layer adjacent to each other and laminated together, the barrier layer being located between the spring layer and the porous fiber layer, The mass layer has a radiation frequency of at least 3 kHz, and the porous fiber layer has an average sound absorption value of at least 0.

40. Noise-reducing trim parts.

2. The sound attenuation trim component according to claim 1, characterized in that the at least one region covers at least 50%, preferably at least 65%, and more preferably at least 80% of the surface of the sound attenuation trim component.

3. The sound attenuation trim component according to claim 1 or claim 2, characterized in that the thickness of the mass layer is substantially constant.

4. The porous fiber layer preferably has at least 35 strokes / cm ２ , more preferably at least 40 strokes / cm ２ More preferably, at least 50 strokes / cm ２ A sound attenuation trim component according to any one of claims 1 to 3, characterized in that it is an air-ray needle-punched porous fiber layer having a needle-punching density.

5. The sound attenuation trim component according to any one of claims 1 to 4, characterized in that the thickness of the porous fiber layer is 2 mm to 10 mm, preferably 3 mm to 8 mm, and more preferably 4 mm to 7 mm.

6. The areal weight of the porous fiber layer is 500 g / m ２ to 2000 g / m ２ , preferably 800 g / m ２ to 1800 g / m ２ , even more preferably 1000 g / m ２ to 1500 g / m ２ The sound attenuation trim part according to any one of claims 1 to 5, characterized in that it is as described above.

7. The barrier layer is 10 g / m² ２ ~200g / m ２ Preferably 50 g / m ２ ~150g / m ２ A sound attenuation trim component according to any one of claims 1 to 6, characterized by having a surface weight.

8. The barrier layer is 500 g / m². ２ ~8000g / m ２ Preferably 1500 g / m² ２ ~5000g / m ２ More preferably 2000 g / m ２ ~3500g / m ２ A sound attenuation trim component according to any one of claims 1 to 7, characterized by having a surface weight.

9. The sound attenuation trim component according to any one of claims 1 to 8, characterized in that the radiation frequency of the mass layer is at least 5000 Hz, preferably at least 6300 Hz.

10. The sound attenuation trim component according to any one of claims 1 to 9, characterized in that the porous fiber layer comprises natural fiber reclaimed fibers, preferably cotton reclaimed fibers, and a binder, preferably a thermoplastic binder, more preferably a thermoplastic binder made of two-component thermoplastic fibers.

11. The sound attenuation trim part according to any one of claims 1 to 9, characterized in that the porous fiber layer includes a thermoplastic two-component filament made of a first polymer having a higher melting point and a second polymer having a lower melting point, preferably a thermoplastic two-component filament made of a terephthalate polyester.

12. The sound attenuation trim component according to any one of claims 1 to 9, characterized in that the porous fiber layer comprises fibers made of terephthalate polyester and a thermoplastic binder, preferably a thermoplastic binder made of polypropylene (PP) fibers.

13. The sound attenuation trim component according to any one of claims 1 to 9, wherein the spring layer, the barrier layer, and the porous fiber layer include materials belonging to the same chemical group, preferably materials belonging to the terephthalate polyester group.

14. A method for manufacturing a sound-attenuating trim component as described in claim 1, comprising at least the following: (a) Laminating the first nonwoven fiber layer, the barrier layer, and the second nonwoven fiber layer on top of each other such that the first nonwoven fiber layer is on top of the barrier layer and the barrier layer is on top of the second nonwoven fiber layer, (b) Placing the multilayer body thus obtained on the lower mold of a molding tool, wherein the molding tool comprises an upper mold and a lower mold that define a cavity having a desired shape for the noise-reducing trim part when closed. (c) Injecting high-temperature steam into the molding tool cavity from both the upper and lower molds in order to harden the fiber layer and bond the fiber layer to the barrier layer, wherein the pressure of the high-temperature steam injected from both the lower and upper molds is first increased from 0 bar to a maximum value, preferably 5 to 6 bar, and then maintained at this maximum value, and in the pressure increase stage of the high-temperature steam pressure, the pressure of the high-temperature steam injected from the lower mold is higher than the pressure of the steam injected from the upper mold, preferably by an amount including 1 to 2 bar, thereby compressing the first porous fiber layer between the barrier layer and the upper mold. (d) After a sufficient time interval for the high-temperature steam to harden the fiber layer and bond the fiber layer to the barrier layer, the steam is discharged through both the upper and lower molds of the molding tool. (e) Open the molding tool and remove the molded part from the molding tool.

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