Multilayer sound absorber, method for producing multilayer sound absorber and use of multilayer sound absorber

Abstract

The invention relates to a multi-layer sound absorber comprising a flow-resistant non-woven fabric having at least two individual flow-resistant layers, the individual flow-resistant layers being arranged one above the other in the direction of penetration of the sound waves to be absorbed and each having a flow resistance of between 300 Pa / m and 1800 Pa / m, preferably between 400 Pa / m and 1500 Pa / m, the flow resistance of the individual flow-resistant layers being greater than the flow resistance of the individual flow-resistant layers being greater than the flow resistance of the individual flow-resistant layers, and the flow resistance of the individual flow-resistant layers being greater than the flow resistance of the individual flow-resistant layers being greater than the flow resistance of the individual flow-resistant layers. And the flow resistance of each independent flow resistance layer is increased layer by layer in the penetrating direction. The invention further relates to a method for producing a multi-layer sound absorber according to the invention and to the use of a multi-layer sound absorber according to the invention for sound absorption in the automotive industry and in the architectural and indoor acoustic fields.

Description

Technical Field

[0001] The invention relates to a multilayer sound absorber according to claim 1. Furthermore, the invention relates to a method for producing a multilayer sound absorber according to claim 13 and to the use of a multilayer sound absorber according to claims 14 and 15. Background Art

[0002] In order to improve the sound absorption of multilayer sound absorbers, increasing thickness and increasing flow resistance are known. In addition, as described in EP3375923A1, multilayer sound absorbers are known, which have a layer of flow-resistant nonwoven fabric with high flow resistance adjacent to another layer with excellent sound absorption.

[0003] However, it has been shown that the known multilayer sound absorbers and the known methods for increasing sound absorption need to be improved in order to limit the product thickness, in particular for low frequencies between 400 and 1250 Hz. In the automotive industry, in particular in the field of electric vehicles, improving the sound absorption in the low frequency range is particularly important, because the tire rolling noise is in this low frequency range and is not masked by the background noise of the internal combustion engine and manual or automatic transmission. In addition, due to the limited installation space, the product thickness of the multilayer sound absorber is very limited in this field. Summary of the invention

[0004] The problem underlying the present invention is therefore to provide a multilayer sound absorber capable of improving the sound absorption in the low frequency range between 400 and 1250 Hz while taking into account limiting the thickness of the product.

[0005] This problem is solved by the features of independent claim 1. Thus, the solution to the problem according to the invention is that a multilayer sound absorber comprises a flow-resistant nonwoven having at least two individual flow-resistant layers, wherein the individual flow-resistant layers are arranged one above the other in the penetration direction of the sound waves to be absorbed and each have a flow resistance between 300 Pa s / m and 1800 Pa s / m, preferably between 400 Pa s / m and 1500 Pa s / m, wherein the flow resistance of each individual flow-resistant layer increases layer by layer in the penetration direction.

[0006] Surprisingly, since the flow resistance of the individual flow resistance layer of the flow resistance nonwoven fabric of the sound absorber in the penetration direction is increased, the sound absorption in the low frequency range can be significantly improved while maintaining the thickness of the entire product unchanged.

[0007] At the same time, it is surprising that the multilayer sound absorber according to the invention has an increased sound absorption even in the very high frequency range above 4000 Hz, while the overall product thickness remains unchanged.

[0008] Preferred embodiments of the invention are subject matter of the dependent claims.

[0009] According to a particularly preferred embodiment of the invention, the difference between the flow resistances of the individual flow resistance layers arranged directly above each other is between 300 and 1500 Pa s / m, preferably between 500 and 1000 Pa s / m. The sudden increase in flow resistance in the above range results in particularly preferred sound absorption in the low frequency range.

[0010] In another particularly preferred embodiment of the invention, the first individual flow resistance layer in the through direction has a flow resistance of at least 400 Pa s / m, preferably a flow resistance between 400 and 700 Pa s / m, and the flow resistance of the second individual flow resistance layer directly adjacent to the first individual flow resistance layer in the through direction is higher than the flow resistance of the first individual flow resistance layer by a value of at least 400 Pa s / m, preferably by a value between 500 Pa s / m and 1100 Pa s / m, and the flow resistance of the second individual flow resistance layer is preferably between 900 and 1700 Pa s / m. First and second individual flow resistance layers of this type enable particularly advantageous sound absorption of the multilayer sound absorber.

[0011] According to another preferred embodiment, the weight per unit area of ​​the separate flow resistance layer is between 20 and 100 g / m 2 Between, preferably between 35 and 85 g / m 2 This weight per unit area is preferred for achieving the necessary flow resistance and the desired thickness of the individual flow resistance layers.

[0012] According to another preferred embodiment, the thickness of the separate flow resistance layer is between 0.1 and 1 mm, preferably between 0.3 and 0.6 mm, which makes the multi-layer sound absorber have a low overall thickness and good sound absorption at the same time.

[0013] In another particularly preferred embodiment of the present invention, the individual flow resistance layers are meltblown nonwovens, wherein at least one of the individual flow resistance layers is manufactured as a meltblown nonwoven without a carrier and without a calender. In this way, the individual flow resistance layers can be manufactured in a preferred manner. At the same time, this manufacturing process allows the high flow resistance of the individual flow resistance layers to be accurately set. Preferably, the individual flow resistance layers are manufactured with a spinning beam having 30 to 80 hpi, particularly preferably 50 hpi. In this case, hpi is the unit "holes per inch".

[0014] According to a particularly preferred embodiment, the flow resistance nonwoven fabric comprises two separate flow resistance layers, wherein the first separate flow resistance layer is configured as a meltblown nonwoven fabric having a unit area weight of 40 g / m 2, with a thickness between 0.43 and 0.47 mm and a flow resistance of 500 Pa s / m, and the second separate flow resistance layer is constructed as a meltblown nonwoven fabric with a unit area weight of 80 g / m 2 The thickness is between 0.53 and 0.57 mm and the flow resistance is 1500 Pa s / m. This type of flow resistance nonwoven fabric can improve the sound absorption of the multi-layer sound absorber in the low frequency range.

[0015] According to another preferred embodiment, the flow resistance nonwoven fabric comprises a mechanically wear-resistant protective nonwoven fabric, which forms the first layer of the flow resistance nonwoven fabric in the penetration direction and has a lower flow resistance than the individual flow resistance layer. This allows the individual flow resistance layer to be protected from mechanical wear without affecting the sound absorption of the multi-layer sound absorber. Preferably, the protective nonwoven fabric is a spunbond nonwoven fabric or a meltblown nonwoven fabric with full-surface calendering. These are two preferred manufacturing variants that can be used to manufacture the protective nonwoven fabric. Further preferably, the protective nonwoven fabric is constructed to have a low flow resistance of less than 500Pa s / m, particularly preferably less than 200Pa s / m. The low flow resistance of the protective nonwoven fabric allows sound waves to pass through in the penetration direction and reach the individual flow resistance layer, and then produce particularly preferred sound absorption there.

[0016] In another preferred embodiment, the flow resistance nonwoven fabric comprises at least three separate flow resistance layers, wherein the difference between the flow resistances of adjacent separate flow resistance layers in the penetration direction decreases. Preferably, the difference between the flow resistances of adjacent separate flow resistance layers in the penetration direction is reduced.

[0017] According to a particularly preferred embodiment, the individual flow-resistance layers of the flow-resistance nonwoven are only regionally connected to one another, so that there are cavities between the individual flow-resistance layers. It has been shown that the cavities between the individual flow-resistance layers can additionally improve the sound absorption in the low-frequency range. Preferably, the individual flow-resistance layers are bonded by a calender, the extrusion surface of the calender being 0.3 to 5%, more preferably 0.4 to 3%, and further preferably 0.6 to 1.2%, wherein the individual flow-resistance layers of the flow-resistance nonwoven are further preferably bonded by a calender at the spaced-apart engraved points forming a pattern. This allows the formation of cavities to a certain extent, which can further improve the sound absorption.

[0018] According to another preferred embodiment, the protective nonwoven and the individual flow resistance layers of the flow resistance nonwoven are only regionally connected to each other, so that there are cavities between the protective nonwoven and the individual flow resistance layers and between the individual flow resistance layers. It has been shown that cavities can further improve the sound absorption in the low-frequency range. Preferably, the protective nonwoven and the individual flow resistance layers are combined by a calender, the extrusion surface of the calender is 0.3 to 5%, more preferably 0.4 to 3%, and even more preferably 0.6 to 1.2%, wherein the protective nonwoven and the individual flow resistance layers of the flow resistance nonwoven are further preferably combined by a calender at the spaced-apart engraving points that form a pattern. This enables the formation of cavities to a certain extent, thereby further improving the sound absorption.

[0019] Preferably, in the above two embodiments, the engraved points generated by the calender form a diamond pattern, a square pattern, a circular pattern or a polygonal pattern, wherein the diamond pattern is particularly preferred. Further preferably, the diameter of the engraved points is between 0.5 and 3 mm, preferably between 1.4 and 2.4 mm, and / or the minimum distance between them is between 5 and 20 mm, preferably between 8 and 15 mm.

[0020] In another preferred embodiment, the multilayer sound absorber has a carrier nonwoven in addition to the flow resistance nonwoven, wherein the carrier nonwoven is laminated to the rear side of the flow resistance nonwoven in the penetration direction and comprises at least first fibers with a fineness of 3 to 28 dtex and second fibers with a fineness of 0.5 to 3 dtex. Preferably, the carrier nonwoven consists of a fiber blend of fibers with a fineness of 0.5 dtex to 28 dtex. Such a combination of a carrier nonwoven and a flow resistance nonwoven enables particularly good sound absorption in the low frequency range while maintaining a low product thickness.

[0021] According to a preferred embodiment, the carrier nonwoven is thermally bonded and / or mechanically bonded and / or has a density of 200 to 1200 g / m 2 Between, preferably 200 to 600 g / m 2 The performance of the carrier nonwoven fabric combined with the flow resistance nonwoven fabric has a positive influence on the performance of the multilayer sound absorber.

[0022] Preferably, the thickness of the carrier nonwoven fabric is 4 to 50 mm, preferably 8 to 35 mm, and more preferably 8 to 25 mm. This type of multilayer sound absorber, having this type of carrier nonwoven fabric in combination with a flow resistance nonwoven fabric, has preferred sound absorption in the low frequency range and at the same time has a thickness such that the multilayer sound absorber can be advantageously used in a limited installation space.

[0023] According to a preferred embodiment, the multilayer sound absorber consists of only one starting material, preferably PET or PBT. This material purity is preferred for reasons of recyclability and ease of disposal.

[0024] In a further particularly preferred embodiment, the total thickness of the multilayer sound absorber is between 5 and 50 mm, preferably between 8 and 35 mm, particularly preferably between 10 and 25 mm. Such a multilayer sound absorber is particularly suitable for limited installation spaces, in particular in the automotive industry, and also achieves preferred sound absorption in the low-frequency range when the available installation space is small.

[0025] Furthermore, the present invention also relates to a method for manufacturing a multi-layer sound absorber according to one of the above-mentioned embodiments, wherein the individual flow resistance layers of the flow resistance nonwoven fabric are arranged one above the other in the penetration direction after manufacturing. In this way, a preferred multi-layer sound absorber can be manufactured.

[0026] According to a preferred embodiment of the method of the invention, the individual flow-resistance layers of the flow-resistance nonwoven are only regionally bonded to one another, so that cavities are formed between the individual flow-resistance layers. Preferably, the individual flow-resistance layers are bonded by a calender having a pressing surface of 0.3 to 10%, more preferably 0.4 to 5%, and even more preferably 0.6 to 1.2%, wherein the calender is more preferably a diamond calender. The protective nonwoven is also particularly preferably bonded to the individual flow-resistance layers of the flow-resistance nonwoven in the same regional manner in the same operating step.

[0027] In another preferred embodiment of the method according to the invention, the individual flow resistance layer of the flow resistance nonwoven is produced as a meltblown nonwoven without a carrier and without a calender. Preferably, the individual flow resistance layer is produced with a spinning beam having a speed of 30 to 80 hpi. In this way, an individual flow resistance layer with a corresponding flow resistance can be produced in a preferred manner.

[0028] According to a further preferred embodiment, the carrier nonwoven is produced parallel to the flow resistance nonwoven, wherein the carrier nonwoven is preferably heat-bonded instead of needle-punched. According to a further preferred embodiment, as the last step of the production process, the carrier nonwoven is laminated on one side to the flow resistance nonwoven. Preferably, an adhesive nonwoven made of the same starting material as the flow resistance nonwoven and the carrier nonwoven is used as an adhesion promoter.

[0029] The invention further relates to the use of a multilayer sound absorber according to one of the above-described embodiments for sound absorption in the automotive industry. Due to the excellent sound absorption in the low-frequency range and the small thickness of the multilayer sound absorber required for this purpose, it is very suitable for sound absorption in the automotive industry. The multilayer sound absorber according to the invention is particularly preferably used in the field of electric vehicles. In this field, the rolling noise of the tires plays an important role in the acoustics of the vehicle interior, because the background noise of the internal combustion engine and the manual or automatic transmission is not masked. These rolling noises are particularly in the low-frequency range, so that the advantageous properties of the multilayer sound absorber according to the invention are particularly prominent.

[0030] Furthermore, the present invention relates to the use of a multilayer sound absorber according to one of the above-described embodiments for sound insulation in the field of building and room acoustics. In this case, it is preferred to increase the sound absorption in the high frequency range above 4000 Hz. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

[0032] The accompanying drawings show:

[0033] Figure 1 is a schematic cross-sectional view of a first embodiment of a multilayer sound absorber according to the present invention,

[0034] Figure 2 A schematic production line of a flow resistance nonwoven fabric according to a first embodiment of a multi-layer sound absorber according to the present invention is shown,

[0035] Figure 3 is a schematic diagram in the penetration direction of the first layer of the first embodiment of the multi-layer sound absorber according to the present invention,

[0036] Figure 4 shows a comparison of the absorption coefficient measured in a reverberation chamber (αcabin) (ISO 354:2003) according to Example A2 of the present invention with Comparative Examples V1 and V2,

[0037] Figure 5 shows a comparison of the absorption coefficients measured in reverberation boxes (ISO 354:2003) of Examples A3, A4 and A5 according to the invention with Comparative Examples V3 and V4, and

[0038] Figure 6 A comparison of the absorption coefficient measured in a reverberation box (ISO 354:2003) according to Example A6 of the present invention and Comparative Example V5 is shown.

[0039] Reference Mark List

[0040] 1 Multi-layer sound absorber

[0041] 2 Penetration direction

[0042] 3 Flow resistance non-woven fabric

[0043] 4 Carrier nonwoven fabric

[0044] 5. First single flow resistance layer

[0045] 6 Second separate flow resistance layer

[0046] 7 Spinning beam

[0047] 8. First unwinding station

[0048] 9 Second unwinding station

[0049] 10 Diamond calender

[0050] 11 Winding Machine

[0051] 12 Protective non-woven fabric

[0052] 13 marking points

[0053] 14 Unbound region

[0054] A2 Second Embodiment

[0055] A3 Third embodiment

[0056] A4 Fourth embodiment

[0057] A5 Fifth embodiment

[0058] V1 First comparative example

[0059] V2 Second comparative example

[0060] V3 Third comparative example

[0061] V4 Fourth comparative example DETAILED DESCRIPTION

[0062] Figure 1 A schematic cross-sectional view of a first embodiment of a multilayer sound absorber 1 according to the invention is shown, wherein the cross section is parallel to the penetration direction 2 of the sound waves to be absorbed by the multilayer sound absorber 1. The cross-sectional view is only schematic. Therefore, the thickness of the individual layers is not shown to scale. The first embodiment of the multilayer sound absorber according to the invention consists of a flow resistance nonwoven 3, which is arranged in front of a carrier nonwoven 4 in the penetration direction 2.

[0063] In this embodiment, the carrier nonwoven fabric 4 is formed into a fiber nonwoven fabric by a fiber blend, the fiber blend is composed of 40% Co-PET fibers with a fiber fineness of 4 den and a length of 51 mm and 60% PET fibers with a fiber denier of 0.9 dtex and a length of 31 mm, and the unit area weight of the fiber nonwoven fabric is 400 g / m 2 And the thickness is 30mm, where the carrier nonwoven fabric is heat-bonded instead of needle-punched.

[0064] In this case, the flow resistance nonwoven fabric 3 is composed of three layers arranged one above the other. In this case, according to the first embodiment, the first layer in the penetration direction 2 is a protective nonwoven fabric 12, which protects the multi-layer sound absorber 1 from mechanical wear and tear, and in this embodiment, it is manufactured with a unit area weight of 19 g / m 2 The layer adjacent to the protective nonwoven fabric 12 in the penetration direction 2 is the first separate flow resistance layer 5. According to this embodiment, the first separate flow resistance layer is a PET meltblown nonwoven fabric with a unit area weight of 40 g / m 2 The flow resistance is 500 Pa s / m and the thickness is between 0.43 and 0.57 mm. The second separate flow resistance layer 6 is adjacent to the first separate flow resistance layer 5 in the penetration direction 2. According to this embodiment, the second separate flow resistance layer is a PET melt-blown non-woven fabric with a unit area weight of 80 g / m 2 , a flow resistance of 1500 Pa s / m and a thickness of 0.53 to 0.57 mm. The three-layer flow resistance nonwoven fabric 3 is combined in specific areas by a diamond calender with an extrusion surface of 0.9%, so that cavities are formed between the layers of the flow resistance nonwoven fabric 3. By the flow resistance nonwoven fabric 3 formed in this way, the flow resistance is gradually increased layer by layer. In combination with the cavities between the layers of the flow resistance nonwoven fabric 3 and the carrier nonwoven fabric 4 to which the flow resistance nonwoven fabric 3 is laminated on one side, this leads to particularly favorable sound absorption in the low frequency range between 400 and 1250 Hz.

[0065] Figure 2 Shown according to Figure 1 Schematic production line of the flow resistance nonwoven fabric 3 of the first embodiment shown. According to the production line, the first individual flow resistance layer 5 is manufactured by meltblowing technology on a spinning beam 7 at 50 hpi. The protective nonwoven fabric 4 is then placed on the first individual flow resistance layer 5 in the first unwinding station 8, and the second individual flow resistance layer 6 is then placed on top in the second unwinding station 9. The three layers arranged in this way are then bonded to each other in a diamond calender 10 with an extrusion surface of 0.9% in a specific area and wound by a winder 11. Then, in a downstream step, one side of the flow resistance nonwoven fabric 3 manufactured in this way can be laminated to the carrier nonwoven fabric 4. In this case, for example, a Co-PET adhesive nonwoven can be used as an adhesion promoter.

[0066] Figure 3 Shown according to Figure 1 A schematic top view of the flow resistance nonwoven 3 and the protective nonwoven 12 of the first embodiment shown in the through-direction 2. They are bonded to the first individual flow resistance layer 5 and the second individual flow resistance layer 6 by means of a diamond calender 10. The diamond calender 10 forms the engraved dots 13 in a diamond pattern. Due to the diamond pattern, these engraved dots 13 are spaced apart and form large non-bonded areas 14. The large non-bonded areas 14 allow the layers of the flow resistance nonwoven 3 to vibrate.

[0067] Figure 4 The absorption coefficient in the frequency range of 400 to 3150 Hz measured in a reverberation box (α-cabin) based on ISO 354:2003 of Example A2 according to the present invention comprising a carrier nonwoven is shown in comparison with Comparative Example V1 comprising only a carrier nonwoven and Comparative Example V2 comprising a carrier nonwoven and a single separate flow resistance layer.

[0068] Example A2

[0069] The multilayer sound absorber according to Example A2 is composed of a carrier nonwoven fabric and three layers of flow resistance nonwoven fabric. In the penetration direction, the flow resistance nonwoven fabric is composed of a first single flow resistance layer, a second single flow resistance layer and a third single flow resistance layer. The first single flow resistance layer is composed of a single layer with a unit area weight of 40 g / m 2 , a melt-blown nonwoven fabric having a flow resistance of 500 Pa s / m and a thickness of 0.32 mm, and a second separate flow resistance layer having a unit area weight of 40 g / m 2 , a PBT meltblown nonwoven fabric having a flow resistance of 1064 Pa s / m and a thickness of 0.34 mm, and a third separate flow resistance layer having a unit area weight of 60 g / m 2 , a PBT meltblown nonwoven fabric with a flow resistance of 1389 Pas / m and a thickness of 0.33 mm. The carrier nonwoven fabric is composed of a fiber nonwoven fabric, which is made of 55% PET-Biko 3den / 51mm and 45% PET 0.9den / 38mm, and the unit weight of the fiber nonwoven fabric is 250g / m 2 The total thickness of the multilayer sound absorber according to Example A2 is 15 mm.

[0070] Comparative Example V1

[0071] Comparative Example V1 is composed of a fiber nonwoven fabric, which is made of 55% PET-Biko 3den / 51mm and 45% PET 0.9den / 38mm, and the weight per unit area of ​​the fiber nonwoven fabric is 250g / m 2 And also has a total thickness of 15mm.

[0072] Comparative Example V2

[0073] In the penetration direction, the comparative example V2 is composed of a single layer of flow resistance nonwoven fabric and a carrier nonwoven fabric, and its unit area weight is 250g / m 2 And also has a total thickness of 15mm, the single-layer flow resistance non-woven fabric is made of PBT melt-blown non-woven fabric, and the unit area weight of the PBT melt-blown non-woven fabric is 60g / m 2 , flow resistance is 1389 Pa s / m and thickness is 0.33 mm, the carrier nonwoven is made of a fiber nonwoven of 55% PET-Biko 3den / 51mm and 45% PET 0.9den / 38mm.

[0074] This comparison clearly shows that in the low frequency range of 400 to 1250 Hz, the sound absorption of the embodiment A2 according to the invention is improved compared with the comparative examples V1 and V2. In this case, the thickness of the three comparative examples is the same. Therefore, the embodiment A2 according to the invention is preferably used as a sound absorber in the low frequency range compared with the comparative examples V1 and V2.

[0075] Figure 5 The absorption coefficients of three embodiments A3, A4 and A5 according to the invention in the frequency range of 400 to 3150 Hz measured in a reverberation box (α-cabin) based on ISO 354:2003 are compared with those of comparative examples V3 and V4.

[0076] Example A3

[0077] The multilayer sound absorber according to Example A3 is composed of three layers of flow resistance nonwoven fabric and a carrier nonwoven fabric. In the penetration direction, the flow resistance nonwoven fabric is composed of a first separate flow resistance layer, a second separate flow resistance layer and a third separate flow resistance layer. The first separate flow resistance layer is composed of a unit area weight of 40 g / m 2 , a melt-blown nonwoven fabric having a flow resistance of 500 Pa s / m and a thickness of 0.32 mm, and a second separate flow resistance layer having a unit area weight of 40 g / m 2 , a PET meltblown nonwoven fabric having a flow resistance of 1064 Pa s / m and a thickness of 0.34 mm, and a third separate flow resistance layer having a unit area weight of 60 g / m 2 , a PET meltblown nonwoven fabric with a flow resistance of 1389 Pas / m and a thickness of 0.33 mm. The carrier nonwoven fabric is composed of a fiber nonwoven fabric, which is made of 20% PET 1.3dtex / 38mm, 25% PET-Biko 4den / 51mm and 55% PET 1.5den / 38mm, and the unit area weight of the fiber nonwoven fabric is 300g / m 2The total thickness of the multilayer sound absorber according to Example A3 is 15 mm.

[0078] Example A4

[0079] The multilayer sound absorber according to Example A4 is composed of three layers of flow resistance nonwoven fabric and a carrier nonwoven fabric. In the penetration direction, the flow resistance nonwoven fabric is composed of a first separate flow resistance layer, a second separate flow resistance layer and a third separate flow resistance layer. The first separate flow resistance layer is composed of a unit area weight of 40 g / m 2 , a PET meltblown nonwoven fabric having a flow resistance of 1064 Pa s / m and a thickness of 0.34 mm, and a second separate flow resistance layer having a unit area weight of 40 g / m 2 , a PET meltblown nonwoven fabric having a flow resistance of 2272 Pa s / m and a thickness of 0.14 mm, and a third separate flow resistance layer having a unit area weight of 60 g / m 2 , a PET meltblown nonwoven fabric with a flow resistance of 3125 Pa s / m and a thickness of 0.20 mm. The carrier nonwoven fabric is composed of a fiber nonwoven fabric, which is made of 20% PET 1.3dtex / 38mm, 25% PET-Biko 4den / 51mm and 55% PET 1.5den / 38mm, and the unit weight of the fiber nonwoven fabric is 300g / m 2 The total thickness of the multilayer sound absorber according to Example A4 is 15 mm.

[0080] Example A5

[0081] The multilayer sound absorber according to Example A5 is composed of three layers of flow resistance nonwoven fabric and a carrier nonwoven fabric. In the penetration direction, the flow resistance nonwoven fabric is composed of a first separate flow resistance layer, a second separate flow resistance layer and a third separate flow resistance layer. The first separate flow resistance layer is composed of a unit area weight of 40 g / m 2 , a melt-blown nonwoven fabric having a flow resistance of 500 Pa s / m and a thickness of 0.32 mm, and a second separate flow resistance layer having a unit area weight of 40 g / m 2 , the flow resistance is 1064Pa s / m, the thickness is 0.34mm, and the third separate flow resistance layer is made of a PET melt-blown non-woven fabric with a unit area weight of 60g / m 2 , a PET meltblown nonwoven fabric with a flow resistance of 1389 Pa s / m and a thickness of 0.33 mm. The carrier nonwoven fabric is composed of a fiber nonwoven fabric, which is made of 40% PET-Biko 4.4dtex / 51mm and 60% PET 0.9dtex / 38mm, and the unit weight of the fiber nonwoven fabric is 300g / m 2 The total thickness of the multilayer sound absorber according to Example A5 is 15 mm.

[0082] Comparative Example V3

[0083] Comparative Example V3 is composed of a fiber nonwoven fabric, which is made of 20% PET 1.3 dtex / 38 mm, 25% PET-Biko 4 den / 51 mm and 55% PET 1.5 den / 38 mm, and the weight per unit area of ​​the fiber nonwoven fabric is 300 g / m 2 And also has a total thickness of 15mm.

[0084] Comparative Example V4

[0085] In the penetration direction, the comparative example V4 is composed of a single layer of flow resistance nonwoven fabric and a carrier nonwoven fabric, and its unit area weight is 300g / m 2 And also has a total thickness of 15mm, the single-layer flow resistance non-woven fabric is made of PET melt-blown non-woven fabric, and the unit area weight of the PBT melt-blown non-woven fabric is 80g / m 2 , the flow resistance is 1550 Pa s / m and the thickness is 0.56 mm, and the carrier nonwoven is made of 20% PET 1.3 dtex / 38 mm, 25% PET-Biko 4den / 51 mm and 55% PET 1.5den / 38 mm.

[0086] Figure 5 The comparison shown also shows that in the low frequency range of 400 to 1250 Hz the sound absorption of the embodiments A3, A4 and A5 according to the invention is improved compared to the comparative examples V3 and V4.

[0087] Figure 6 A comparison of the absorption coefficient in the frequency range of 400 to 10,000 Hz measured in a reverberation chamber (α-cabin) based on ISO 354:2003 of Example A6 according to the invention and Comparative Example V6 comprising a carrier nonwoven and a single separate flow resistance layer is shown.

[0088] Example A6

[0089] The multilayer sound absorber according to Example A6 is composed of a carrier nonwoven fabric and three layers of flow resistance nonwoven fabric. In the penetration direction, the flow resistance nonwoven fabric is composed of a protective nonwoven fabric, a first separate flow resistance layer and a second separate flow resistance layer, and the protective nonwoven fabric has a unit area weight of 19 g / m 2 , a spunbonded nonwoven fabric with a flow resistance of <200 Pa s / m and a thickness of 0.10 mm, the first separate flow resistance layer having a unit area weight of 40 g / m 2, a PBT meltblown nonwoven fabric with a flow resistance of 500 Pa s / m and a thickness of 0.45 mm, and a second separate flow resistance layer with a unit area weight of 80 g / m 2 , a PBT meltblown nonwoven fabric with a flow resistance of 1500 Pa s / m and a thickness of 0.56 mm. The carrier nonwoven fabric is composed of a fiber nonwoven fabric, which is made of 70% PET-Biko4den / 51mm, 20% PET 12den / 64mm and 10% PET 11dtex / 60mm hollow fibers, and the unit area weight of the fiber nonwoven fabric is 1000g / m 2 And the flow resistance is 256 Pa s / m. The total thickness of the multilayer sound absorber according to Example A6 is 12 mm.

[0090] Comparative Example V5

[0091] In the penetration direction, the comparative example V5 is composed of a single layer of flow resistance nonwoven fabric and a carrier nonwoven fabric, and its unit area weight is 1000 g / m 2 The air flow resistance is 256 Pa s / m and also has a total thickness of 12 mm. The single-layer flow resistance non-woven fabric is made of PBT melt-blown non-woven fabric, and the unit area weight of the PBT melt-blown non-woven fabric is 80 g / m 2 , the flow resistance is 5350 Pa s / m and the thickness is 0.22 mm, and the carrier nonwoven fabric is made of a fiber nonwoven fabric of 70% PET-Biko 4den / 51mm, 20% PET 12den / 64mm and 10% PET 11dtex / 60mm hollow fibers.

[0092] This comparison clearly shows that in the low frequency range of 400 to 1250 Hz, the sound absorption of the example A6 according to the invention is improved compared to the comparative example V5. However, at the same time, the comparison also shows that in the very high frequency range between 4000 and 10000 Hz, the sound absorption of the example A6 according to the invention is significantly improved compared to the comparative example V5. The thickness of the comparative examples is the same. Thus, the example A6 according to the invention is more preferably used as a sound absorber in the low frequency range and in the very high frequency range than the comparative example V5.

Claims

1. A multi-layer sound absorber comprising a flow-resistant nonwoven fabric having at least two separate flow-resistant layers, wherein: The individual flow resistance layers are arranged up and down in the penetration direction of the sound waves to be absorbed, and each has a flow resistance between 300Pa s / m and 1800Pa s / m, preferably between 400Pa s / m and 1500Pa s / m, wherein the flow resistance of each of the individual flow resistance layers increases layer by layer in the penetration direction.

2. The multi-layer sound absorber according to claim 1, characterized in that: The difference between the flow resistances of the individual flow resistance layers arranged directly above each other is between 300 and 1500 Pa s / m, preferably between 500 and 1000 Pa s / m.

3. The multi-layer sound absorber according to claim 1 or 2, characterized in that: The first individual flow resistance layer in the penetration direction has a flow resistance of at least 400 Pa s / m, preferably a flow resistance between 400 and 700 Pa s / m, and the flow resistance of the second individual flow resistance layer directly adjacent to the first individual flow resistance layer in the penetration direction is higher than the flow resistance of the first individual flow resistance layer by at least 400 Pa s / m, preferably by a value between 500 Pa s / m and 1100 Pa s / m, wherein the flow resistance of the second individual flow resistance layer is preferably between 900 and 1700 Pa s / m.

4. The multi-layer sound absorber according to any one of claims 1 to 3, characterized in that: The unit area weight of the separate flow resistance layer is 20 to 100 g / m 2 Between, preferably between 35 and 85 g / m 2 and / or the thickness of the separate flow resistance layer is between 0.1 and 1 mm, preferably between 0.3 and 0.7 mm.

5. The multi-layer sound absorber according to any one of claims 1 to 4, characterized in that: The individual flow resistance layers are meltblown nonwovens, wherein at least one of the individual flow resistance layers is produced as a meltblown nonwoven without a carrier and without a calender, and wherein the individual flow resistance layers are preferably produced with a spinning beam having a spinning speed of 30 to 80 hpi, particularly preferably 50 hpi.

6. The multi-layer sound absorber according to any one of claims 1 to 5, characterized in that: The flow resistance non-woven fabric comprises a protective non-woven fabric resistant to mechanical wear, which forms the first layer of the flow resistance non-woven fabric in the penetration direction and has a lower flow resistance than the separate flow resistance layer, wherein the protective non-woven fabric is preferably a spunbond non-woven fabric or a meltblown non-woven fabric with full-surface calendering, and is also preferably formed with a low flow resistance of less than 500 Pa s / m, particularly preferably less than 200 Pa s / m.

7. The multi-layer sound absorber according to any one of claims 1 to 6, characterized in that: The flow resistance nonwoven fabric includes at least three individual flow resistance layers, wherein the difference between flow resistances of the individual flow resistance layers adjacent to each other decreases in the penetration direction.

8. The multi-layer sound absorber according to any one of claims 1 to 7, characterized in that: The individual flow-resistance layers of the flow-resistance nonwoven are bonded to one another only in regions such that cavities remain between the individual flow-resistance layers, wherein the individual flow-resistance layers are preferably bonded by a calender having a pressing surface of 0.3 to 5%, more preferably 0.4 to 3%, and further preferably 0.6 to 1.2%, wherein the individual flow-resistance layers of the flow-resistance nonwoven are preferably bonded by the calender at spaced-apart engraved points forming a pattern.

9. The multi-layer sound absorber according to any one of claims 1 to 8, characterized in that: The multilayer sound absorber has a carrier nonwoven fabric in addition to the flow resistance nonwoven fabric, wherein the carrier nonwoven fabric is laminated on the rear side of the flow resistance nonwoven fabric in the penetration direction and includes at least first fibers with a fineness of 3 to 28 dtex and second fibers with a fineness of 0.5 to 3 dtex.

10. The multi-layer sound absorber according to claim 9, characterized in that: The carrier nonwoven is thermally bonded and / or mechanically bonded and / or has a density of 200 to 1200 g / m 2 Between, preferably 200 to 600 g / m 2 The weight per unit area is between .

11. The multi-layer sound absorber according to any one of claims 1 to 10, characterized in that: The multilayer sound absorber consists of only one starting material, preferably PET or PBT.

12. The multi-layer sound absorber according to any one of claims 1 to 11, characterized in that: The total thickness of the multi-layer sound absorber is between 5 and 50 mm, preferably between 8 and 35 mm, and particularly preferably between 10 and 25 mm.

13. A method for producing a multilayer sound absorber according to any one of claims 1 to 12, wherein: The individual flow resistance layers of the flow resistance nonwoven fabric are arranged one above the other in the penetration direction after production, and are only partially bonded to each other in such a manner that cavities remain between the individual flow resistance layers.

14. Use of the multilayer sound absorber according to one or more of claims 1 to 13 for sound absorption in the automotive industry.

15. Use of the multilayer sound absorber according to one or more of claims 1 to 13 for sound insulation in the field of building and room acoustics.

Images