Firewall

Abstract

The invention relates to an acoustic component contoured in a planar manner or three-dimensionally shaped, namely a firewall of a motor vehicle, and use of said component, said component comprising at least one sound-absorbing material and possibly at least one carrier material, wherein the sound-absorbing material is completely or partially covered by a flow layer at least on a planar side or in a composite of layers, wherein the flow layer has nanofibers.

Claims

1. A three-dimensionally shaped acoustically effective firewall of a motor vehicle comprising at least one three-dimensionally shaped absorber with one or more layers that is covered on at least one major surface thereof by a flow layer on the entire surface or partially, which flow layer is directly applied to the absorber and consists of nanofibers, wherein the flow resistance of the flow layer is equal or different in a locally defined way, said flow layer is sandwiched between several loosely stacked or compressed layers and said absorber, the thickness of said firewall is equal throughout its area or different in a locally defined way, said nanofiber layer has a flow resistance that is different in a locally defined way over the component, the firewall further comprises a support material open to flow, wherein said support open to flow with the absorber and the flow layer comprises several loosely stacked or compressed layers.

2. The firewall according to claim 1, characterized in that said absorber material is covered on both major surfaces on the entire surface or partially with said flow layer.

3. The firewall according to claim 1, characterized by comprising a layer composite of from 2 to 5 layers of the absorber and of the flow layer.

4. The firewall according to any of claim 1, characterized in that the flow resistance of the flow layer(s) is from 500 Ns/m.sup.3 to 100,000 Ns/m.sup.3.

5. The firewall according to claim 1, characterized in that said flow layer is applied to one side of said support open to flow, which is provided on the absorber and/or functions as a coating.

6. The firewall according to claim 1, characterized in that said support open to flow with the absorber and the flow layer comprises from 3 to 7 loosely stacked or compressed layers.

7. The firewall according to claim 1, characterized in that said nanofiber layer has a flow resistance that is uniform over the component.

8. The firewall according to claim 1, wherein the firewall is used at a distance to a solid wall.

9. The firewall according to claim 1, wherein the firewall is used at a distance to an adjacent component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is illustrated and described herein with reference to the various drawings, in which like reference numbers denote like method steps and/or system components, respectively, and in which:

(2) FIG. 1 illustrates the firewall of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) The present invention describes acoustic components, namely firewalls, consisting of an absorptive material, optionally in a layer composite, and optionally support and intermediate layers, which are covered with a very lightweight and acoustically homogeneous flow layer, especially consisting of nanofibers, completely, i.e., on both sides, or partially, i.e., on one side thereof and/or on selected surface areas of one or both sides of the sound-absorbing material. The nanofiber layer (flow layer) can be applied directly to the absorber material (sound-absorbing material) on the one hand, or using a support layer, on the other. Also, said nanofiber layer may be present between different absorber material and support layers.

(4) In an essential embodiment, the absorber of the firewall is formed from foam, bonded fibers, bonded foam particles, or a mixture thereof, optionally in a layer composite, three-dimensionally in accordance with the component contour, and covered with nanofibers throughout the surface on one side thereof or completely.

(5) In another preferred embodiment, the absorber material is not bonded, and is present between two circumferentially contacting textile supports open to flow and having a coating containing nanofibers.

(6) For the use between two walls, the support layer that is open to flow is shaped in such a way that a wall gap is formed at least on one side, preferably on both sides. Said gap is mostly within a range of 1 mm (net air gap) and/or about three quarters of the available building space. Optionally, the lightweight acoustic component may fill the entire building space.

(7) In the above mentioned embodiment, the coating (the nanofiber layer) is defined in such a way that over the area, a uniform or defined varying basis weight, i.e., one that is unequal partially over the area, and thus locally different flow resistances are formed.

(8) The majority of acoustically effective components in vehicles is two-dimensional, mostly contoured two-dimensional, has a three-dimensional and essentially flat shape and contacts the car body, so that a partial coating with nanofibers is fully purposeful in such cases. Of course, for components in a cavity, a full-area nanofiber coating, i.e., one provided on both sides, is also useful.

(9) As a loose as well as bonded/shaped filler material, the known absorber materials are employed: synthetic fibers, especially polyester fibers, polyamide fibers, especially nylon 6 and/or nylon 66; polyolefin fibers, especially PP and/or PE; acrylic fibers and their fiber mixtures including bicomponent fibers and multicomponent fibers and/or mixtures of natural fibers, especially raw cotton, hemp, cocoa, kenaf, jute and/or sisal fibers, with the above mentioned synthetic fibers; animal, metallic or inorganic fibers as well as materials mainly functioning as spacers (spacer knittings, particle foam, etc.); further PUR foam.

(10) As a blank material and as a material for molded parts, except for the materials serving as spacers, the same materials can be employed, which are bonded, however, through binder materials (BiCo fibers, plastic powders), or mechanical bonding (needling, stitching).

(11) Textile sheets open to flow or three-dimensional textile structures, such as woven fabrics, loop-formingly knitted fabrics, loop-drawingly knitted fabrics, braiding, stitch-bonded fabrics, non-woven fabrics and felts as well as the three-dimensional textile structures (body structures), such as textile tubes, are employed as the support layer.

(12) The materials for textile supports are dependent on the application field: plastic materials (PA, PP, PET, aramids, etc.); natural fibers (linen, cotton, etc.), inorganic and metallic fibers (glass, carbon, aluminum, etc.).

(13) A broad range of materials is available as nanofibers. There can be employed almost all plastic materials; as well as fibers based on natural materials, and metallic and inorganic fibers. Nanofibers within the meaning of the present invention include, in particular, fibers having a fiber diameter of smaller than 900 nanometers (nm), preferably within a range of from 50 to 800 nm, more preferably from 75 nm to 300 nm.

(14) According to the invention, nanofibers are preferably processed in or on a composite non-woven and on three-dimensionally predeformed components.

(15) For synthetic fiber non-wovens, this means that they are combined already during the preparation, for example, by electrospinning, with other methods, such as melt spinning and others, and thus can form a composite with microfibers. In addition, support or protection non-wovens may be included additively in said micro-nano fiber composite, so that a composite non-woven is formed. In glass fiber mats, the nozzle blowing method for preparing air filter non-wovens with nanoscale fibers is widespread.

(16) In the claimed acoustic components, namely the firewall, the basis weight of the nanofibers is preferably from 0.01 g/m.sup.2 to 15 g/m.sup.2, especially from 0.2 g/m.sup.2 to 1.5 g/m.sup.2, based on the flow layer.

(17) The flow resistance of the flow layer is preferably from 500 Ns/m.sup.3 to 100,000 Ns/m.sup.3, more preferably from 3,000 Ns/m.sup.3 to 20,000 Ns/m.sup.3. For components with a complete area coverage, the flow resistances should be in the upper range and may be equal or different for each side.

(18) Through the height of the flow resistance, the ratio of absorptive to isolating effect of the component can be adjusted.

(19) The present invention improves the homogeneity of the pore distribution by using nanofibers for forming the flow layer, thereby shifting the scale for describing both the size of the cavities and their relative arrangement to smaller dimensions. If the specific flow resistance of the flow layer is too high, the sound cannot penetrate into the backside absorber and is reflected in a wide area. The component essentially behaves as an insulator. If the flow resistance of the flow layer is very low (open), essentially only the absorber is acting.

EXAMPLES

Example 1/Comparative Example 1

(20) The application of the invention shall be demonstrated for components according to the invention.

(21) In a first application, a firewall of the prior art for a luxury car with a spring-mass structure consisting of a commercially available elastic foam and a commercially available thermoplastic heavy layer with an average basis weight of 4 kg/m.sup.2 was replaced by a so-called dual impedance structure.

(22) The dual impedance structure consists of a core prepared in a fiber injection method and consisting of a fiber mixture with 20% by weight PET BiCo fibers, 40% by weight cotton recycling fibers, and 40% by weight PET fibers. The support non-woven consists of a 40 g/m.sup.2 PET non-woven and is uniformly coated with 0.8 g/m.sup.2 PA nanofibers (continuous fibers). The support non-woven with nanofibers (of the flow layer) was press-bonded onto the fiber absorber by means of a commercially available PE adhesive at 20 g/m.sup.2 at a temperature above the melting temperature of the PE. The thus prepared firewall was lighter by about 5 kg than the serial firewall, and by only 0.5 points worse than the serial firewall in a subjective evaluation in a rating within the scope of a driving test. With a locally limited mass density, the same acoustic effect could be achieved with a saving in weight of 3 kg.

Example 2

(23) In another application, a three-dimensionally shaped absorber prepared in a fiber injection method and consisting of 25% by weight PET BiCo fibers, 40% by weight cotton recycling fibers and 35% by weight PET fibers was applied directly on one side with a 0.6 g/m.sup.2 PA nanofiber coating, the flow layer.