LIGHT WEIGHT ACOUSTIC TRIM PART

Abstract

Multilayer sound attenuating trim part for a vehicle, in particularly for a trim part or cladding used in the interior of a car, for instance as an inner dash or as part of the floor covering or for the exterior of a vehicle, for instance as a trim part or cladding in the engine bay area or as part of an under body trim part as well as to the method of producing a part, comprising at least two fibrous layers (10, 30) and at least one air permeable intermediate film layer (20) between the at least two fibrous layers, whereby all layers together have a variable thickness.

Claims

1. Multilayer Automotive trim part for noise attenuation comprising at least 2 fibrous layers and at least one air permeable intermediate film layer between the at least 2 fibrous layers, whereby all layers together have a variable thickness characterized in that at least for an area with a thickness between 4 and 12.5 mm the overall air flow resistance (AFR.sub.overall) and the overall density ρ relate as follows 1500<AFR.sub.overall−10ρ<3800 with AFR.sub.overall in Nsm.sup.−3 and ρ in kg/m.sup.3.

2. Multilayer Automotive trim part for noise attenuation comprising at least 2 fibrous layers and at least one air permeable intermediate film layer between the at least 2 fibrous layers, whereby all layers together have a variable thickness characterized in that at least for an overall density above 250 kg/m.sup.3 the overall air flow resistance (AFR.sub.overall) and the overall density ρ relate as follows 1500<AFR.sub.overall−10ρ <3800 with AFR.sub.overall in Nsm.sup.−3 and ρ in kg/m.sup.3.

3. Automotive trim part according to claim 1, wherein the air flow resistance of the top layer and the intermediate layer together represents at least 55% of the overall AFR of the multilayer, preferably between 65% and 80% of the overall AFR of the multilayer.

4. Automotive trim part according to claim 1, wherein the AFR of the intermediate film layer is higher than the AFR of the at least 2 fibrous layers.

5. Automotive trim part according claim 1, wherein at least one of the fibrous layers comprises a mixture of fibers consisting of 10 to 40% by weight of binder fibers, 10 to 70% by weight of recycled fibers and 10 to 70% by weight of self-crimped fibers wherein the total amount of said fibers adds to 100% by weight.

6. Automotive trim part according to claim 1, wherein at least one of the fibrous layers comprises a mixture of fibers consisting of 10 to 40% by weight of binder fibers, 10 to 70% by weight of recycled fibers wherein the total amount of said fibers adds to 100% by weight.

7. Automotive trim part according to claim 1, wherein at least one of the fibrous layers comprises a mixture of fibers consisting of 10 to 40% by weight of binder fibers, 10 to 70% by weight of recycled fibers and 10 to 70% by weight of synthetic fibers wherein the total amount of said fibers adds to 100% by weight.

8. A multilayer acoustic trim part according to claim 1, wherein the air permeable intermediate film layer is one of a single layer film or a multilayer film.

9. A multilayer acoustic trim part according claim 8, wherein the film is made with at least one of the following polymers: copolymer or polymer of acetate, like Ethylene Vinyl Acetate (EVA), copolymers of acrylate for instance Ethylene Acrylic Acid (EAA), a polyolefin for instance a polyethylene (PE) based polymer, like linear density polyethylene (LDPE), linear long density polyethylene (LLDPE) or a metallocene linear long density polyethylene (mLLDPE) or derivatives, or a multilayer film, preferably a combination of a polyethylene based copolymer film covered with an adhesive EAA layer at least at one side.

10. A multilayer acoustic trim part according to claim 1, wherein the film is replaced by one of: a nonwoven scrim, a hot melt layer, a gluing web or adhesive layer.

11. A multilayer acoustic trim part according to claim 1, wherein the binder fibers are one of a mono-component fiber or bi-component fiber made with at least one of the following materials, polyester, in particularly polyethylene terephthalate, polyolefins, in particularly Polypropylene or polyethylene, polylactic acid (PLA) or polyamide.

12. A multilayer acoustic trim part according to claim 1, wherein the recycling fibers are one of a cotton shoddy, a synthetic shoddy, a polyester shoddy, a natural fiber shoddy, or a mixed synthetic fiber and natural fiber shoddy.

13. A multilayer acoustic trim part according to claim 1, wherein the self-crimped or synthetic fibers are made with at least one of the following materials polyamide (nylon) preferably polyamide 6 or polyamide 6,6, polyester and or its copolymers, preferably polyethylene terephthalate or polybutylene terephthalate, or polyolefin, preferably polypropylene or polyethylene, or made of a polymer and its copolymer, preferably polyethylene terephthalate and its copolymer.

14. A multilayer acoustic trim part according to claim 1, wherein the self-crimped fibers are conjugate fibers made of at least 2 sides with a difference between the two sides inducing an intrinsic self-crimping of the fiber in a random 3 dimensional form.

15. A multilayer acoustic trim part according to claim 1, further comprising at least one of a covering scrim layer, an acoustic scrim layer, a decorative top layer, for instance a tufted carpet layer or nonwoven carpet layer.

16. Use of the multilayer acoustic trim part according claim 1, as an interior trim part for instance as an inner-dash, as part of an interior flooring system, or as an inner wheel house lining or as an acoustic cladding, or as an engine bay trim part, for instance a hood liner or outer-dash.

Description

[0032] In an embodiment the trim part is made with at least 2 fibrous layers, and an intermediate film layer whereby at least one of the fibrous layers is a mixture of fibers consisting of 10 to 40% by weight of binder fibers, 10 to 70% by weight of recycled fibers and 10 to 70% by weight of self-crimped fibers.

[0033] In another embodiment the trim part is made with at least 2 fibrous layers and an intermediate film layer whereby at least one of the fibrous layers is a mixture of fibers comprising of 10 to 40% by weight of binder fibers and 10 to 70% by weight of recycled fibers. Preferably 10 to 70% by weight of synthetic fibers might be included in this layer.

[0034] Surprisingly the combination of material in at least one of the fibrous layers according to the embodiments further optimises the acoustic performance. It enables to reduce weight and still obtain the variable thickness needed for this type of automotive trim parts, normally in the range of between 4 and 30 mm, preferably up to 35 mm. However depending on material of the at least one layer up to 40-50 mm total thickness can be achieved, for instance with at least one layer containing self-crimped fibers.

[0035] The top fibrous layer, the layer facing away from the source of noise, for instance the body in white, has preferably an area weight of between 250 and 1800 gsm (grams per square meter), preferably between 400 and 1000 gsm.

[0036] Preferably the thickness of the top layer is between 1 and 10 mm in the final trim part. Preferably this layer has a more constant thickness.

[0037] The second layer facing towards the source of noise, for instance the body in white, has preferably an area weight of between 250 and 1500 gsm, more preferably between 300 and 800 gsm.

[0038] Preferably the thickness of the second layer is between 2 and 60 mm in the final trim part.

[0039] The overall area weight of the at least 2 fibrous layers is preferably between 800 and 2500 gsm, preferably between 1000 and 2000 gsm.

[0040] In particular by the combination of the materials as claimed, it is possible to obtain the higher thicknesses required to fill the packaging space and surprisingly the area with the lower thicknesses still shows acoustic absorption, thereby increasing the area with effective acoustic absorbing properties to almost 100%. With the materials according to the invention an increase in initial thickness at reduced density could be achieved, therefore a reduction in weight at same thickness can be achieved. This is an advantage for the car maker as the part becomes lighter in weight, having a direct positive effect on the fuel consumption and the CO.sub.2 footprint of the car.

[0041] Surprisingly the initial resilience of the material is kept mainly intact during the production and even during prolonged use of the material. This is beneficial as the trim parts or cladding made with the material are normally in the car throughout their lifetime, the product will therefore maintain its initial performance longer.

[0042] The air-permeable intermediate film layer is either a single layer film or a multilayer film. The film may be cast or blown film preferably. The intermediate film layer preferably has a thickness of between 5 and 100 gsm, more preferably between 8 and 50 gsm, even more preferably between 8 and 40 gsm.

[0043] The film can be made from at least one of the following polymers:

[0044] copolymer or polymer of acetate, like Ethylene Vinyl Acetate (EVA), copolymers of acrylate for instance Ethylene Acrylic Acid (EAA), a polyolefin for instance a polyethylene (PE) based polymer, like linear density polyethylene (LDPE), linear long density polyethylene (LLDPE) or a metallocene linear long density polyethylene (mLLDPE) or derivatives, or a multilayer film, preferably a combination of a polyethylene based copolymer film covered with an adhesive EAA layer at least at one side.

[0045] The intermediate layer is air-permeable at least in the final product, enhancing the overall air flow resistance of the trim part. Depending on the process chosen for laminating the layers and moulding the final part the film might be air permeable from the beginning, or might become air permeable during the production of the part. If the film is made air permeable in a separate production step, it should be chosen such that the film enhances the overall air flow resistance of the part.

[0046] A preferred process is opening the film layer during the moulding of the trim part using steam pressure to obtain an air permeable layer with an air flow resistance that is beneficial for the overall acoustic performance of the part. By opening the film during the final production step of the trim part the AFR properties of the film may be tuned to the required needs.

[0047] Preferably the intermediate layer is the layer with the highest air flow resistance.

[0048] Preferably the air flow resistance of the thin intermediate layer is between 500 and 2500 N.s.m.sup.−3 in the final product independent of the process chosen.

[0049] The air permeable intermediate layer can alternatively be one of a nonwoven scrim, a hot melt layer, a gluing web or adhesive layer that after moulding has the same level of air flow resistance as would be achieved with the film material.

[0050] In some cases, the second layer can be peeled off from the overall construction, while the first layer and the intermediate layer are more difficult to separate.

[0051] Preferably the air flow resistance of the top layer and the intermediate layer together represents at least 55% of the total AFR of the complete multilayer, preferably between 65% and 80% of the total AFR of the complete multilayer.

[0052] The trim part comprises at least 2 fibrous layers of which at least one of the layers is made from a mixture of fibers consisting of 10 to 40% by weight of binder fibers, 10 to 70% by weight of recycled fibers and 10 to 70% by weight of self-crimped fibers.

[0053] The other layer preferably comprises at least a mixture of 10 to 40% binder fibers and 10 to 90% recycled fibers. However this layer might also benefit from added self-crimped fibers or synthetic fibers.

[0054] Self-crimped fibres are fibres with two sides, arranged such that one side has shrinked differently from the other side and thereby induced a shaping of the filament away from the straight line, for instance in the form of spiral, omega or helical. However in most cases the shape is not necessarily a regular structure: irregular 3 dimensionally shaped versions are having the same advantage.

[0055] Self-crimped fibers can be made by exploiting morphology differences across the fiber either by utilizing the inherent morphology differences of two different polymers or by creating a morphology difference in a homopolymer by means of additives or process manipulation. Methods to achieve this include but are not limited to bicomponent technologies such as side by side and eccentric sheath core, which exploits molecular weight and/or stereochemistry differences of each component. Similar effects can be achieved by manipulating other melt spinning process variables (i.e. melt viscosity) that cause a differential in the orientation level across the fiber diameter, while using a homopolymer. Additionally, polymer additives like cross linkers or branching agents could also be used to create a similar effect.

[0056] A pre-requisite for self-crimping is a certain crimping potential created by differences in shrinkage, shrinking power and modulus of elasticity of the two fiber components.

[0057] A mechanical crimp might be used to further enhance the fiber crimp and the shape formed, for instance by including a stuffier box treatment or a saw tooth gear treatment.

[0058] Self-crimped fibers differ from mechanically crimped fibers in a way that they obtain the crimping capacity during the spinning of the fiber as an intrinsic feature of the fiber. This intrinsic self-crimp is less likely to be lost during further production process steps or later use of the material. The crimp in self-crimped fibers is permanent.

[0059] The advantages of using a self-crimped fiber rather than a mechanically crimped fiber are manifold. For the invention as disclosed the most important advantages are that the fiber is in the crimped status from the beginning of the production of the fibrous layers. The crimped status in the form of a randomly 3-dimensional shaped fiber is the preferred status of the fiber. Surprisingly, the fiber stays in this preferred shape during the whole production as well as during the lifetime of the trim part. Mechanically crimp on its own is less strong and will lose its' properties over time. Mechanically crimped fibers will flatten out over time, losing the resilience and loftiness, making the trim part to fail over time in its purpose.

[0060] The self-crimped fiber is preferably a side by side conjugate fiber. Preferably the conjugate material is chosen such that there is a difference in viscosity causing an inherent self-crimping in the fibre. However other types of conjugate fibers that show a self-crimping as defined might be chosen as well.

[0061] Fibers that have a crimping potential that is induced later by an additional process for instance an heating step, are defined as having latent crimp. This crimp can also be obtained by the same type of differences as previously disclosed. Preferably the self-crimped fibers are in their final crimped status, and no further crimping is induced by later processes. To have the crimped status from the beginning of the production of the automotive trim part, shows a better mixing of the fibers, a more homogenous fibrous mat after carding or airlay, and less crimp of the fibrous mat during moulding therefore the blank size can be estimated more precisely. While inducing crimp during thermal moulding of the trim part, would result in a heavy crimp of the fibrous mat, causing a movement of the fibers during moulding, which might result in faults in the final part. Depending on the 3 D shape of the trim part, there is no benefit in a too late initiation of the shrinkage of the fibers.

[0062] Overall the use of the self-crimped fibers enhances the evenness of the material layer obtained by for instance carding methods or more preferred air laying methods. The natural tendency of the self-crimped fibers to go back to a random curled form gives the fibers an additional resilience. In particularly the shoddy material is not clumping again during processing and is better spread throughout the layer.

[0063] Surprisingly the material as claimed can be thermoformed more precisely in a 3 D shape and in addition the resilience of the material is not substantially reduced during moulding, showing that the fibers are less prone to deterioration during the moulding process of the actual part. In addition, the material keeps its resilience during use, ergo the initial thickness obtained directly after moulding is maintained longer.

[0064] Preferably, the self-crimped fibers are made of one or a combination of: [0065] polyamide (nylon) preferably polyamide 6 or polyamide 6,6, in short PA; [0066] polyester and or its copolymers, for instance polyethylene terephthalate in short PET; polybutylene terephthalate, in short PBT, or [0067] polyolefin, for instance polypropylene, (PP) or polyethylene (PE) [0068] or a combination of a polymer and its copolymer as mentioned, for instance a combination of polyethylene terephthalate and copolyethylene terephthalate PET/CoPET.

[0069] The use of polyesters is most preferred as they have a good record of recycling. The polymers used can be virgin or coming from recycled resources, as long as the material requirements are given.

[0070] Preferably the self-crimped fibres have an overall round cross section, more preferably with a hollow core, also known as hollow conjugate fibers. However, other cross-sections known in the art to make conjugate self-crimped fibers can be used as well.

[0071] The synthetic fibers of one of the embodiments might have a circular cross section, preferably hollow, or other cross section beneficial to the overall bulkiness of the fibrous material. For instance a hollow hexagonal cross section, or a hollow winged cross section. Other cross-sections might work as well.

[0072] Both the synthetic and self-crimped fibers might have 2 or multiple hollow cavities in the length direction of the fiber.

[0073] The 2 sides, components or polymers should be distributed in the filament string such that a difference in shrinkage is given. The maximum crimp may be developed when the fibers are comprised of equal parts of each component and the components were separated and located on opposite sides of the fiber.

[0074] The staple fibre length of self-crimped fibers used is preferably between 32 and 76 mm. The fiber is preferably between 2 and 20 dtex, more preferably between 2 and 10 dtex.

[0075] The binder fibers for any of the fibrous layers can be one of a mono-component fiber or bi-component fiber made with at least one of the following materials, polyester, in particularly polyethylene terephthalate, polyolefins, in particularly Polypropylene or polyethylene, polylactic acid (PLA) or polyamide (PA) in particularly polyamide 6 or polyamide 6.6. The binder fibers are preferably between 10 and 40% by weight of the total fibers for any of the fibrous layers.

[0076] The recycling fibers are preferably shoddy cotton, shoddy synthetic, shoddy polyester or shoddy natural fibers, whereby the shoddy type is defined by having at least 51% by weight of the material included, 49% can be fibers from other sources. So for instance, a shoddy polyester contains at least 51% by weight of polyester based materials. Alternatively, the shoddy material can be a mixture of different synthetic and natural fibers, whereby not one type is prevailing.

[0077] The fibrous layer not including the crimped fibers or the layer facing towards the source of noise, might include other natural or synthetic types of fibers common in the industry, for instance wool, abaca, polyolefin, for instance polypropylene or polyethylene, or polyester, for instance polyethylene-terephthalate (PET) or a mixture of such fibers. This layer might also include ultrafine fibers in the range from 0.5 to 2 dtex.

[0078] Preferably the fibrous layers are having the same or similar mixture of fibers.

[0079] The at least 2 fibrous layers may be compressed differently to form layers with different properties. They may differ in at least one of: stiffness, density, air flow resistance or fibre mixture, or a combination of these properties, to further optimise the absorbing properties of the trim part.

[0080] In a preferred embodiment the trim part is to be placed in a car to cover a vehicle panel to reduce noise. The side of the trim part that is facing in the direction of the passenger compartment, away from the vehicle panel (the top fibrous layer), may have a higher stiffness than the side that is facing in the direction of the vehicle panel (the second fibrous layer). This side is preferable following the body in white and has loftier properties.

[0081] Preferably, the at least 2 fibrous layers and the intermediate film layer together have an overall density of between 20 and 460 kg/m.sup.3. The variable overall density can be achieved preferably by compression of the at least 2 fibrous layers and the intermediate layer during the moulding of the trim part to form the required shape, resulting in a product that is overall air permeable and functions as an acoustic absorbing trim part that is light weight and keeps its structure during the lifetime of the product.

[0082] The trim part has a variable thickness. At least for the area of the part having a thickness between 4 and 12.5 mm the overall air flow resistance and overall density follows the relation 1500<AFR.sub.overall−10ρ<3800.

[0083] Furthermore at least for the areas with overall density of between 200 and 500 kg/m.sup.3 the overall air flow resistance and overall density follow the relation 1500<AFR.sub.overall−100ρ<3800.

[0084] Preferably the relation is fitting the area of the part for a thickness of above 4 mm or an overall density of below 500 kg/m.sup.3 and more preferably for a thickness below 25 mm or an overall density of above 20 kg/m.sup.3. Thereby enabling that almost 100% of the trim part contributes to the noise attenuation, even at a reduced weight of the part.

[0085] FIG. 1 is showing schematically the set-up of the product according to the claim with the at least 2 fibrous layers 10 and 30 and the thin intermediate film layer 20. Blanks of the fibrous layers and the intermediate layer are stacked as indicated in figure A and the stack of materials is moulded to form a trim part with a 3 dimensional shape shown as an example in figure B. During the moulding the top and/or bottom fibrous layers are compressed and the fibers are bound to set the final shape of the part. Optionally as part of the process the intermediate film layer might become air-permeable, for instance by forming micro perforations or by the process of melting and solidifying of the material. Although layer 10 after moulding is relatively constant in its final thickness, slight variations in thickness might be given. In this example, the lower layer 30 has a more pronounced 3 dimensional shape to enable a good fit to the body-in-white of the car. Preferably, at least the layer directed to the body in white of the car comprises crimped fibers as claimed.

[0086] An example of a part according to invention can be as follows:

[0087] The top layer 10 is facing away from the noise source and is made of a first fibrous layer with an area weight of 750 gsm comprising 18% of PET/CoPET bicomponent fibers as binder fibers and 82% of recycled fibers, preferably a shoddy cotton.

[0088] The air permeable intermediate layer 20 is a film layer with a thickness of between 19 gsm. The film layer is made permeable during the steam moulding process of the part, thereby fine tuning the air flow resistance of the film using steam pressure.

[0089] The second fibrous layer 30 is a fibrous layer with an area weight of 550 gsm consisting of 18% by weight of PET/CoPET bicomponent fibers as binder fibers and 40% by weight of PET conjugated self-crimped fibers and 42% of recycled fibers, preferably cotton shoddy.

[0090] Giving an overall area weight of around 1300 gsm.

[0091] An comparative example according to the state of the art has a top layer of 18% bicomponent fibers as binder fibers and 82% of shoddy material with an area weight of 750 gsm, roughly the same film layer and a second fibrous layer of the same material as the top layer, however at 1100 gsm to compensate for thickness requirements of the trim part. As this material does not achieve the required initial thickness to fill the maximum thickness areas of the part at a lower area weight. Hence the part has a total area weight of 1850 gsm.

[0092] FIG. 2 is showing a simulation of the acoustic performance for the same trim part optimised according to the invention as claimed. The absorption is based on actual measurements in an Alpha Cabin of flat samples and on the thickness distribution as mentioned in the background section. The absorption of a part according to the state of the art is shown in dotted line, while the absorption of a part according to the invention is shown in continuous line. The better acoustic performance for the part according to the invention is specifically linked to the performance in the areas of low thickness (high density) which is better for the part according to the invention because of the optimal overall AFR.

[0093] The multilayer part according to invention can be used as an interior trim part for instance as an inner-dash, or hush panel, as part of an interior flooring system, as an acoustic cladding, or as an engine bay trim part, for instance a hood liner, or outer-dash or as an outer or inner wheel arch liner.

[0094] A multilayer acoustic trim part according to the invention may further comprise additional layers such as a covering scrim layer, an acoustic scrim layer, a decorative top layer, for instance a tufted or nonwoven carpet layer. To keep the benefit of the acoustic attenuation these additional layers should be air permeable at least on the side directed to the noise source.

The Production of the Trim Part

[0095] In the following possible production processes will be explained in more detail. However, a skilled person might also be expected to know how to use alternative processes to come to a similar result.

[0096] The different fibres are blended in the advantageous combination according to the teachings of the invention and the properties needed for the specific part, such that the fibers are evenly blended throughout the material formed. The blended fibres are formed in a mat or bat, by known technologies available on the market. Preferably by using a card or garnet, which gives a more orientated fibre material or by using an air-lay process, for instance using a Rando-Webber or other known air lay machine, which gives a more random laid web or mat. The thus obtained web or mat can be further processed in a continuous process. If there is a need for later processing the web or mat formed can be consolidated for instance in a thermal process step or by using needling. Needling is not preferred for the fibrous webs or mats containing the self-crimped fibers, since it has a negative impact on the loftiness and resilience of the layer obtained.

[0097] The product can be made by using hot and/or cold moulding processes. An example of such a process can be a combination of preheating the material in a hot air oven followed by a cold moulding step to obtain the 3 D shaped trim part. Alternatively the material is heated directly in the mould for instance by a hot fluid, like hot air or steam, to obtain a consolidated part. In particular, the use of steam is preferable if the film is to be made air permeable during the moulding step.