Sound-absorbing structure and manufacturing method thereof

Abstract

To obtain a sound absorbing structure having superior sound absorbing properties by using thinner and lighter materials. [Solution] The hollow plate material has side walls that stand in the thickness direction and divide the cells, and upper and lower walls that are provided at the edges of the side walls, and one of the upper and lower walls has a structure in which a plurality of openings are formed. A skin layer made of a film-like material and having smooth surfaces on both sides is laminated on the main surface of the hollow plate material in which a plurality of cells are arranged side by side, and the surface of the skin layer is covered with a resin and has a density of 5 to 200 mg / cm. 3 and a nonwoven fabric layer having a thickness of 0.5 to 20.0 mm, which are welded together via an intermediate layer having one or more of the structures set forth in A to C below. A: An intermediate layer formed by some of the fibers of the nonwoven fabric layer being embedded in the skin layer while maintaining their fiber shape. A: An intermediate layer having a structure in which some fibers of the nonwoven fabric layer are melted and adhered to the surface of the skin layer. C: An intermediate layer having a structure in which the surface of the skin layer and some of the fibers of the nonwoven fabric layer are once melted and mixed together.

Description

[Technical Field]

[0001] The present invention relates to a sound absorbing structure and a method for manufacturing the same. [Background technology]

[0002] Patent Document 1 describes a sound-absorbing structure that is a hollow structure in which a plurality of cells are arranged upright, and in which a plurality of through holes are formed on the upper surface of the hollow structure, and a nonwoven fabric layer is provided to improve sound absorption performance. However, as described in the examples, the nonwoven fabric layer is provided by "attaching." Judging from the word "attached," it means that it is attached with an adhesive or pressure-sensitive adhesive, and does not disclose any other means or structure. Patent Document 2 describes a composite sound-absorbing material that is made by stacking a sound-absorbing layer such as urethane foam or glass wool, a shielding plate, and a protruding plate from above, and has holes that penetrate the sound-absorbing layer and the shielding plate. Patent Document 3 describes a two-layer laminate consisting of a thermoplastic synthetic resin layer containing a fiber reinforcement material and a nonwoven fabric layer made of two types of fiber. In producing the laminate, the entire nonwoven fabric layer is heated and pressurized together with the thermoplastic synthetic resin layer by heating during compression molding. Patent Document 4 describes a laminated nonwoven fabric that can be used for air filters, liquid filters, vacuum cleaner filters, etc., in which specific thermoplastic long fiber layers are used as upper and lower layers and a specific thermoplastic fine fiber layer is used as an intermediate layer, and the layers are integrated by point bonding using thermal bonding. Patent Document 5 describes a composite nonwoven fabric for sound absorption, in which a staple fiber nonwoven fabric containing crimped hollow fibers and a sound-absorbing film layer made of a synthetic resin film are laminated by heat fusion. In particular, it is essential to use a staple fiber nonwoven fabric containing crimped hollow fibers, and does not suggest that other melt-laminated nonwoven fabrics, such as laminating them to a film layer with a hot melt adhesive, can also be used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-65026 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-194649 [Patent Document 3] International Publication No. 2012-164977 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-121261 [Patent Document 5] Japanese Patent Application Laid-Open No. 2015-174398 Summary of the Invention [Problem to be solved by the invention]

[0004] The sound-absorbing structures described in the above patent documents have been able to achieve a certain degree of improvement in sound absorption. However, the characteristics are still insufficient. Moreover, the invention described in Patent Document 4 is a laminate that is intended for use in air filters, liquid filters, vacuum cleaner filters, etc., and is designed to actively allow gas to pass through, but is not intended to provide excellent sound absorption. The object of the present invention is to obtain a sound-absorbing structure with even better sound-absorbing properties using thinner, lighter materials. [Means for solving the problem]

[0005] 1. A hollow plate material having a side wall portion erected in the thickness direction to divide cells, and an upper wall portion and a lower wall portion provided at the edge of the side wall portion, and one of the upper wall portion and the lower wall portion has a structure in which a plurality of openings are formed, and a skin layer made of a film-like material having smooth surfaces on both sides is laminated on the main surface of the hollow plate material in which a plurality of cells are arranged side by side, and the surface of the skin layer and a resin made of a resin and having a density of 5 to 200 mg / cm 3 and a nonwoven fabric layer having a thickness of 0.5 to 20.0 mm, which are welded together via an intermediate layer having one or more of the structures set forth in A to C below. A: An intermediate layer formed by some of the fibers of the nonwoven fabric layer being embedded in the skin layer while maintaining their fiber shape. A: An intermediate layer having a structure in which some fibers of the nonwoven fabric layer are melted and adhered to the surface of the skin layer. C: An intermediate layer having a structure in which the surface of the skin layer and some of the fibers of the nonwoven fabric layer are both melted and mixed together. 2. The sound-absorbing structure according to 1, wherein the skin layer has a plurality of holes formed therein. 3. The sound-absorbing structure described in 2, wherein the inner diameter distribution of the holes on the surface of the skin layer provided on one of the wall portions facing the nonwoven fabric layer is such that, when the average inner diameter is set to 100, 30% to 70% of the total number of holes have inner diameters that are 80% to 120% of the average inner diameter. 4.A. A side wall portion that stands in the thickness direction and divides the cells, and an upper wall portion and a lower wall portion that are provided at the edge of the side wall portion, One of the upper wall portion and the lower wall portion has a structure in which a plurality of openings are formed, and a skin layer surface formed by laminating a skin layer made of a film-like material having smooth surfaces on both sides on a main surface of a hollow plate material in which a plurality of cells are arranged side by side; and / or the skin layer side of a nonwoven fabric layer made of resin fibers; heating the B. A step of pressing the surface of the skin layer and the skin layer side of the nonwoven fabric layer together; in order, The skin layer is laminated on the main surface of a hollow plate material in which a plurality of cells are arranged side by side, and the surface of the skin layer and a resin-made sheet having a density of 5 to 200 mg / cm 3 A method for producing a sound-absorbing structure having a structure in which a nonwoven fabric layer having a thickness of 0.5 to 20.0 mm is welded to the sound-absorbing structure via an intermediate layer having one or more of the structures described in A to C below. A: An intermediate layer in which some of the fibers of the nonwoven fabric layer are embedded in the skin layer while maintaining their fiber shape. A: An intermediate layer having a structure in which some of the fibers of the nonwoven fabric layer are once melted and adhered to the surface of the skin layer. C: An intermediate layer having a structure in which the surface of the skin layer and some of the fibers of the nonwoven fabric layer are once melted and mixed together. 5.C. A step of heating the surface of the skin layer made of a film-like material having smooth surfaces on both sides and / or the skin layer side of the nonwoven fabric layer made of resin fibers; D. A step of pressure-bonding the surface of the skin layer and the skin layer side of the nonwoven fabric layer to obtain a laminate via an intermediate layer having one or more of the following structures A to C: E. The skin layer side surface of the obtained laminate; The laminated laminated sheet comprises a side wall portion extending in a thickness direction to partition cells, and an upper wall portion and a lower wall portion provided at the edge of the side wall portion, The hollow plate material has a side wall portion that stands in the thickness direction and divides the cells, and an upper wall portion and a lower wall portion that are provided at the edge of the side wall portion, and one of the upper wall portion and the lower wall portion has a structure in which a plurality of openings are formed, and the main surface of the hollow plate material in which a plurality of cells are arranged side by side is laminating step; containing The skin layer is laminated on the main surface of a hollow plate material in which a plurality of cells are arranged side by side, and the surface of the skin layer is made of resin fibers and has a density of 5 to 200 mg / cm 3 A method for manufacturing a sound-absorbing structure having a structure in which a nonwoven fabric layer having a thickness of 0.5 to 20.0 mm is welded. A: An intermediate layer in which some of the fibers of the nonwoven fabric layer are embedded in the skin layer while maintaining their fiber shape. A: An intermediate layer having a structure in which some of the fibers of the nonwoven fabric layer are once melted and adhered to the surface of the skin layer. C: An intermediate layer having a structure in which the surface of the skin layer and some of the fibers of the nonwoven fabric layer are once melted and mixed together. [Effects of the Invention]

[0006] The present invention involves laminating nonwoven fabrics so as to form and fix a specific intermediate layer formed on the skin layer, thereby enabling the nonwoven fabric layer to be provided more reliably, and the sound-absorbing structure to be thinner than conventional structures while still providing excellent sound-absorbing properties. Furthermore, even when processed into a three-dimensional shape after lamination, the skin layer and the nonwoven fabric layer will not peel off from each other. [Brief explanation of the drawings]

[0007] [Figure 1](a) is a perspective view of only the core layer and skin layer of the sound-absorbing structure of the first embodiment, (b) is a cross-sectional view along the α-α line of (a) with a nonwoven fabric layer provided, and (c) is a cross-sectional view along the β-β line of (a) with a nonwoven fabric layer provided. [Figure 2] 1 is a diagram showing an embodiment of welding a skin layer and a nonwoven fabric while forming an intermediate layer in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] An example of the sound absorbing structure of the present invention will be described below with reference to FIG. (Overview of hollow board material with multiple cells arranged side by side and skin layer) FIG. 1(a) shows the sound-absorbing structure of the present invention, in which a skin layer 30 and a nonwoven fabric layer are not provided, and a hollow plate material (hereinafter referred to as "core layer or core layer 20") having a plurality of cells arranged in a row is laminated on its main surface, and holes 15 are formed to connect the core layer 20 to the outside of the sound-absorbing structure. The sound-absorbing structure is composed of a core layer 20 having a plurality of cells S arranged in a row inside, a film-like or sheet-like skin layer 30 with smooth surfaces on both sides bonded to the upper surface of the core layer 20, and a sheet-like skin layer 40 bonded to the lower surface of the core layer 20. In the present invention, the core layer 20 and the skin layers 30, 40 may both be made of a thermoplastic resin, or only one of them may be made of a thermoplastic resin. Furthermore, the core layer 20 and the skin layers 30, 40 are made of a resin sheet rather than a woven or nonwoven fabric. This main surface refers to the side of the sound source that is the object of sound absorption when the sound absorbing structure of the present invention is used.

[0009] As shown in FIGS. 1(b) and 1(c), the core layer 20 may be formed by folding a single thermoplastic resin sheet formed into a predetermined shape. The core layer 20 is composed of an upper wall portion 21, a lower wall portion 22, and side wall portions 23 that are erected between the upper wall portion 21 and the lower wall portion 22 and define cells S (S1 and S2 in the figure) in the shape of hexagonal columns. The upper and lower wall portions are provided so as to cover the cells S from above and below. The size of the cells S is not particularly limited, but it is preferable that the distance between opposing sides of the regular hexagonal cross-sectional shape of the cells S is approximately 5 to 20 mm. The height of the cells S in the thickness direction of the sound absorbing structure 10 is, for example, preferably approximately 5 to 40 mm, and more preferably approximately 10 to 30 mm. The thickness of a single thermoplastic resin sheet material for forming the core layer is not particularly limited, but is a fraction to a few tenths of the thickness of the formed core layer (preferably 0.2 to 5.0 mm, more preferably 0.2 to 3.0 mm, and even more preferably 0.3 to 2.0 mm). Shinsa

[0010] As shown in FIGS. 1(b) and 1(c), the cells S formed within the core layer 20 include a first cell S1 and a second cell S2, each having a different structure. As shown in FIG. 1(b), the first cell S1 has a two-layer upper wall portion 21 provided on the upper part of the side wall portion 23. The layers of this two-layer upper wall portion 21 are bonded to each other. The first cell S1 also has a single-layer lower wall portion 22 provided on the lower part of the side wall portion 23. On the other hand, as shown in FIG. 1(c), the second cell S2 has a single-layer upper wall portion 21 provided on the upper part of the side wall portion 23. The second cell S2 also has a two-layer lower wall portion 22 provided on the lower part of the side wall portion 23. The layers of this two-layer lower wall portion 22 are bonded to each other. As shown in FIGS. 1(b) and 1(c), adjacent first cells S1 and adjacent second cells S2 are each separated by a two-layer side wall portion 23. In FIG. 1(a), the upper wall portion 21 and the lower wall portion 22 of the core layer 20 are shown as having a single-layer structure.

[0011] As shown in FIG. 1(a), the first cells S1 are arranged in a row along the X direction, and when viewed from above, two adjacent first cells S1 share one side of a hexagon. Similarly, the second cells S2 are arranged in a row along the X direction, and when viewed from above, two adjacent second cells S2 share one side of a hexagon. The rows of first cells S1 and the rows of second cells S2 are alternately arranged in the Y direction, which is perpendicular to the X direction. The first cells S1 and second cells S2 form a honeycomb structure as a whole in the core layer 20.

[0012] In addition, it is preferable that the sheet is non-breathable from the viewpoint of improving sound insulation. 3 The weight of the sheet body is preferably 1000 g / m or more. 2 The above is preferable. The higher the specific gravity of the sheet body, the more significant the increase in sound loss transmission effect can be obtained from the low frequency range. Note that the low frequency range referred to here generally refers to the range of 200 Hz to 400 Hz. The same applies to the following explanation.

[0013] The core layer in the present invention is not limited to the above-described core layer. It is sufficient if the core layer can be used for sound absorption, and the cross section in a plane parallel to the core layer surface may be any shape, such as a honeycomb shape consisting of a hexagon, a rectangle, a triangle, an irregular shape, or a circle. The cross section in a plane perpendicular to the core layer surface may be a quadrilateral such as a rectangle, a square, or a trapezoid, or any other irregular shape. In addition to the skin layer of the present invention, a thin layer may be formed on one or both sides of the core layer. When the skin layer has holes in the thickness direction of the layer, it is preferable that the thin layer also has holes at positions that match the holes in the skin layer in order to obtain excellent sound absorption. The skin layer does not have to have holes.

[0014] As shown in Figures 1(a) to 1(c), a skin layer 30 is bonded to the upper surface of the core layer 20, and a skin layer 40 is bonded to the lower surface of the core layer 20, thereby constituting the sound-absorbing structure 10. Therefore, the upper wall portion 21 of the core layer 20 and the skin layer 30 are provided at the upper edge of the side wall portion 23 of the core layer 20, thereby closing the cells S. Similarly, the lower wall portion 22 of the core layer 20 and the skin layer 40 are provided at the lower edge of the side wall portion 23 of the core layer 20, thereby closing the cells S. When a nonwoven fabric layer is not provided on the surfaces of the skin layer 30 and the skin layer 40 via an intermediate layer, the skin layer itself may or may not be provided. Note that in Figures 1(b) and 1(c), of the three cells S shown, the leftmost cell S is representatively numbered, but the same applies to the other cells S. In this case, the upper wall portion 21 and the lower wall portion 22 may be formed in conjunction with the formation of the core layer 20, which is formed by folding a single thermoplastic resin sheet material molded into a predetermined shape, as shown in Figures 1(b) and 1(c). In this case, the thickness of the upper wall portion 21 and the lower wall portion 22 may be independently the thickness of one or two thermoplastic resin sheets. The upper wall portion 21 and the lower wall portion 22 in Figures 1(b) and 1(c) are each formed so that they have a thickness equivalent to the thickness of two thermoplastic resin sheets folded.

[0015] As shown in Figures 1(b) and 1(c), holes 15 that allow communication between the inside and outside of the cells S are provided on the top surface 10a of the sound-absorbing structure 10. Specifically, as shown in Figure 1(b), in the first cell S1, the holes 15 are provided so as to penetrate the upper skin layer 30 and the two-layered upper wall portion 21. Furthermore, as shown in Figure 1(c), in the second cell S2, the holes 15 are provided so as to penetrate the upper skin layer 30 and the single-layered upper wall portion 21. In other words, the holes 15 are provided in the closing walls of each cell S that close the upper portions of the side wall portions 23.

[0016] In FIG. 1, a plurality of holes 15 are formed so as to be aligned in the vertical and horizontal directions of the skin layer 30 (the X and Y directions in FIG. 1(a)). The holes 15 are regularly formed so that the formation pitch in both the vertical and horizontal directions is equal to each other. The formation pitch of the holes 15 may be smaller than the formation pitch of the cells S, or may be about 1 / 5 to 5 / 5 or about 1 / 5 to 3 / 5 of the formation pitch of the cells S. Therefore, a plurality of holes 15 are formed for one cell S of the core layer 20. The formation pitch of the cells S refers to the distance between the centers of adjacent cells S that share one side of a hexagon. The pitch at which the holes 15 are formed may be the same as the pitch at which the cells S are formed. In this case, the holes can be formed at the same positions in the skin layer of each cell.

[0017] The shape of the holes 15 is not particularly limited, but may be round, rectangular, or irregular when viewed from above. Furthermore, the size of the holes 15 is not particularly limited, but from the viewpoint of good sound absorption of the sound absorbing structure, the holes 15 preferably have a diameter of about 1 / 20 to 1 / 5 of the distance between opposing sides of the regular hexagonal cross-sectional shape of the cells S. For example, the diameter of the holes 15 is preferably about 0.25 to 4.0 mm, and more preferably about 0.5 to 1.5 mm. The inner diameter distribution of the pores on the surface of the skin layer provided on one wall portion facing the nonwoven fabric layer may be such that, when the average inner diameter is 100, 30% to 70% of the total number of pores have an inner diameter that is 80% to 120% of the average inner diameter. This average inner diameter is the average pore diameter of the surface portion of the skin layer of 300 randomly selected pores 15.

[0018] Pores with such a distribution of inner diameters can be achieved by adjusting the conditions for the process of welding the surface of the skin layer and the nonwoven fabric to form the intermediate layer. In this welding process, the skin layer and / or the nonwoven fabric are melted and pressurized so that the skin layer and the nonwoven fabric are integrated via the intermediate layer by welding. The molten resin then flows into the pores through their openings, partially blocking the pore openings, resulting in the above-described inner diameter distribution of the pore openings. Alternatively, after the nonwoven fabric is welded to the surface of the skin layer, holes may be formed in these layers.

[0019] 1(b) and 1(c), when the formation pitch of the holes 15 is the same as the formation pitch of the cells S, the holes 15 are formed at the same positions in the first cell S1 and the second cell S2. Then, the multiple holes 15 formed in the skin layer 30 are formed at the same positions as the first holes 15a formed in the cells. If the pitch at which the holes 15 are formed is smaller than the pitch at which the cells S are formed, a plurality of holes may be formed in one cell S.

[0020] After the skin layer 30 is formed, when a hole 15 is formed by perforating it with a needle or the like to connect the inside and outside of the cell S, the hole 15 has a structure consisting of the skin layer 30 bent convexly as a convex body toward the inside of the cell S and the upper wall portion 21, as shown in Figures 1(b) and (c). The thickness of the skin layer is not particularly limited as long as it has sufficient strength for welding to the nonwoven fabric, but is preferably 0.2 to 5.0 mm, more preferably 0.2 to 3.0 mm, and even more preferably 0.3 to 2.0 mm.

[0021] (Nonwoven fabric layer with intermediate layer) The sound-absorbing structure of the present invention has a structure in which a nonwoven fabric layer made of resin fibers is laminated on a skin layer 30 provided on a main surface of the core layer 20, with an intermediate layer formed by welding a nonwoven fabric (not shown in FIG. 1(a)) interposed therebetween (hereinafter, this may be simply referred to as a "nonwoven fabric layer"). When the skin layer 30 is provided on the upper wall portion 21 provided on the core layer 20 as described above, and the upper wall portion 21 is formed from an unfolded thermoplastic resin sheet material, a surface layer consisting essentially of two layers (the upper wall portion 21 consisting of one layer and the skin layer) is formed on the surface of the core layer 20. When the upper wall portion 21 is formed by folding a thermoplastic resin sheet material as shown in FIG. 1(b), a surface layer consisting essentially of three layers (the upper wall portion 21 consisting of two layers and the skin layer) is formed on the surface of the core layer 20.

[0022] In the present invention, the nonwoven fabric before being laminated on the skin layer is referred to as the nonwoven fabric, and the portion of the nonwoven fabric that retains its structure after lamination is referred to as the nonwoven fabric layer. Each fiber constituting the nonwoven fabric may be solid, may have holes, or may be hollow (tubular). However, in consideration of the welding strength and sound absorption properties of the nonwoven fabric, it is desirable for the fibers to be solid. The nonwoven fabric is preferably composed of fibers only, but may also be composed of fibers and a binder such as a resin. However, if a resin binder is contained or the fibers constituting the nonwoven fabric are combined so as to have two or more different melting points, and the resin forming the intermediate layer is mainly composed of fibers with a lower melting point, then although lamination to another member becomes easier, sound absorption properties tend to decrease. Furthermore, given its structure, the sound-absorbing structure of the present invention is not intended to be subsequently subjected to processing involving heating, such as hot pressing, to form folded portions with large curvatures, as shown in the drawings of WO 2012 / 164977. However, even if processing involving heating is performed, the fibers forming the nonwoven fabric layer do not have a melting point that would melt the entire nonwoven fabric layer during processing.

[0023] 2(a) to 2(c) are schematic cross-sectional views of the sound absorbing structure after the nonwoven fabric layer is provided. The entire layer of the nonwoven fabric before the intermediate layer is formed is not used for forming the intermediate layer, but only a portion of the surface of the nonwoven fabric facing the skin layer is used for forming the intermediate layer. Even if the nonwoven fabric is formed before being welded onto the skin layer, after welding, the layer is a mixture of fibers and some of the resin of the nonwoven fabric that has been melted once, across the entire thickness direction of the nonwoven fabric, and is pressure-molded at the same time as being heated for melting. The layer of nonwoven fabric formed on the skin layer together with the melted resin is not the nonwoven fabric layer of the present invention. Even when a nonwoven fabric layer is provided on the skin layer 30 via an intermediate layer, a nonwoven fabric layer may or may not be provided on the skin layer 40 side. When a nonwoven fabric layer is not provided on the skin layer 40 side, the skin layer 40 may or may not be provided.

[0024] The thickness of the nonwoven fabric layer is not particularly limited, but is preferably 0.5 mm or more, more preferably 2.0 mm or more, and even more preferably 4.0 mm or more, and is preferably 20.0 mm or less, more preferably 17.0 mm or less, and even more preferably 15.0 mm or less. The sound-absorbing structure of the present invention is not obtained by leaving the thickness of the nonwoven fabric used as is, but rather by using a portion of the thickness to form an intermediate layer. Since 5 to 90% of the thickness of the nonwoven fabric used is used to form the intermediate layer, the thickness of the nonwoven fabric layer after obtaining the sound-absorbing structure will be 10 to 95% of the thickness of the nonwoven fabric used. Furthermore, even if a nonwoven fabric layer is provided on the surface of the skin layer via an intermediate layer using each of the following methods, the nonwoven fabric is laminated in such a way that the above-mentioned pores 15 originally present in the skin layer are not blocked by the molten skin layer and / or the intermediate layer made of molten nonwoven fabric fibers. Furthermore, the nonwoven layer is not subjected to pressure forming during the process of laminating the nonwoven to the skin layer, which would alter the shape of the laminate.

[0025] The density of the nonwoven fabric and the nonwoven fabric layer is 5 mg / cm 3 or more than 10 mg / cm 3 On the other hand, it is desirable that the concentration is 200 mg / cm or more. 3 or less than 100 mg / cm 3 It is desirable that the density is 5 mg / cm or less. 3 If the density is less than 200 mg / cm, it is difficult to sufficiently improve the performance of the porous sound absorbing material. 3 If the thickness exceeds this value, it becomes difficult to create a lightweight sound absorbing structure. 5 mg / cm 3 or more and 100 mg / cm 3 If the thickness is less than this, the sound absorbing structure can be made thinner and the sound absorbing characteristics can be improved over a wide frequency range from medium to high frequencies.

[0026] The sound-absorbing structure of the present invention is not one in which the skin layer and the nonwoven fabric are simply laminated in contact with each other, nor is it one in which the skin layer and the nonwoven fabric are laminated via another layer such as an adhesive.Furthermore, it is not one in which the fibers on the surface of the nonwoven fabric are welded at points to the surface of the skin layer. The structure of the nonwoven fabric layer formed by laminating a nonwoven fabric to a skin layer via an intermediate layer may be a structure having an intermediate layer with nonwoven fabric fibers embedded in the surface of the skin layer, as shown in Figure 2(a), a structure having an intermediate layer formed by welding the surface of a partially melted nonwoven fabric to the surface of the skin layer, as shown in Figure 2(b), or a structure having both of these structures, i.e., a structure having an intermediate layer formed by melting the surface of the nonwoven fabric and the surface of the skin layer, with the melted portions of each being mixed together, as shown in Figure 2(c).

[0027] For example, these structures can be selected and formed by adjusting the relationship between the melting points of the skin layer and the nonwoven fabric and the temperature at which they are heated, as follows. When the pores in the skin layer are open to the spaces in the core layer, it is necessary to consider the heating temperature and the material and structure of the skin layer so that the open pores are not substantially blocked even after the nonwoven fabric layer is formed on the skin layer. To form holes in the skin layer, a nonwoven fabric layer may be formed on the surface of the skin layer, and then a needle or the like may be inserted through these layers. The sound-absorbing structure of the present invention can be used for purposes other than wall materials, vehicle components, and flooring, or as a flooring material. However, when used as a flooring material, the nonwoven fabric layer is not oriented toward the underside of the flooring material, and the nonwoven fabric layer is not installed so as to improve adhesion with an adhesive applied to the surface of the floor substrate.

[0028] (Middle layer structure) The intermediate layer in the present invention is a layer having one or more of the following structures A to D. In none of the layers is there point contact between the skin layer and the nonwoven fabric layer. A. An intermediate layer formed by embedding some of the fibers of the nonwoven fabric layer in the skin layer while maintaining their fiber shape. When the melting point of the nonwoven fabric is higher than that of the skin layer (or the nonwoven fabric is not thermoplastic), and the heating temperature of the skin layer surface exceeds the melting point of the skin layer but is lower than the melting point of the nonwoven fabric, the structure has an intermediate layer formed by the ends of the fibers that make up the nonwoven fabric entering the once-melted skin layer. In this case, the structure of the intermediate layer has a state in which the ends of the fibers that make up the nonwoven fabric have penetrated into the skin layer while maintaining the shape of the fibers.

[0029] A. An intermediate layer having a structure in which some of the fibers of the nonwoven fabric layer are melted and adhered to the surface of the skin layer. When the melting point of the fibers of the nonwoven fabric is lower than that of the skin layer and the heating temperature is between these melting points, the ends of the fibers of the nonwoven fabric melt and are welded to the surface of the skin layer via the newly formed intermediate layer. The structure of the intermediate layer in this case is such that the ends of the fibers constituting the nonwoven fabric melt once and then form a solidified layer, which exists on top of the original skin layer.

[0030] C. An intermediate layer having a structure in which the surface of the skin layer and some of the fibers of the nonwoven fabric layer are melted and mixed together. When the heating temperature is higher than the melting points of the skin layer and the nonwoven fabric, the contacting surfaces of the skin layer and the nonwoven fabric melt together to form an integrated layer, forming a newly formed intermediate layer. The structure of this intermediate layer is such that both the ends of the fibers constituting the nonwoven fabric and the skin layer melt once, and at least a portion of the molten material becomes compatible and integrated. These intermediate layers themselves may not have through holes, or the diameter of the through holes that the skin layer had may be smaller. They do not form a breathable layer structure, such as a vacuum cleaner filter, where multiple fiber layers are simply point-bonded together. Since the intermediate layer is derived from part of the skin layer and / or part of the nonwoven fabric layer and is not a layer consisting of only two or more fiber layers, even if the intermediate layer has pores, the pores have a diameter that is similar to or smaller than the pores in the original skin layer.

[0031] When a laminated structure is constructed with a skin layer and a nonwoven fabric layer interposed between them, vibrations from the sound source vibrate the fibers that make up the nonwoven fabric layer, and these vibrations are then reliably transmitted through the intermediate layer to the skin layer, which is integrated with the ends of the fibers. This vibration can then be expected to be directly and uniformly spread throughout the skin layer. As a result, the addition of a hollow core layer provides a higher sound absorption coefficient and / or the ability to absorb sounds over a wider frequency range. In this way, the sound absorbing structure of the present invention can exhibit superior sound absorbing properties over a wider frequency range. This effect is superior to structures in which the skin layer and nonwoven fabric are simply in contact. Simply stacking the skin layer and nonwoven fabric makes it difficult for vibrations generated by sound absorption by the nonwoven fabric to be transmitted to the core layer. Furthermore, even if an adhesive layer is formed between the skin layer and nonwoven fabric to bond the two layers, the presence of the adhesive layer makes it difficult for vibrations of the nonwoven fabric fibers transmitted from the sound source to be transmitted to the core layer.

[0032] Furthermore, as described above, the holes 15 on the surface of the skin layer on one wall facing the nonwoven fabric layer have a certain range of inner diameter distribution, so that in addition to the excellent sound absorption properties described above, sound can be absorbed more reliably even if the sound to be absorbed consists of a particularly wide range of frequencies. However, as an embodiment in which a nonwoven fabric layer and a skin layer are integrated, a fiber-containing resin layer consisting of a single layer formed by uniformly incorporating fibers into a resin is not used.

[0033] Furthermore, an adhesive layer or a pressure-sensitive adhesive layer may or may not be provided between the skin layer and the nonwoven fabric layer. If an adhesive layer or a pressure-sensitive adhesive layer is provided, these materials may fill holes formed in the skin layer before lamination, which may result in difficulty in improving sound absorption. Furthermore, the layer may become excessively thick or may peel off over long periods of use. When holes are formed after the skin layer and nonwoven fabric layer are bonded with an adhesive, the tool used to make the holes, such as a needle, moves perpendicular to the main surface of the hollow plate. If the adhesive layer is flexible, there is a concern that the needle and the tool may move at the same time. This can result in partial peeling of the nonwoven fabric from the skin layer. As a result, it is difficult for the vibrations generated by the sound absorption of the nonwoven fabric to be transmitted reliably to the core layer.

[0034] (Materials that make up each layer) As described above, the core layer 20 and the skin layers 30 and 40 are preferably made of resin. The nonwoven fabric layer F contains a resin. The resin may be any conventionally known thermoplastic resin, and examples thereof include polyolefin resins such as polyethylene resin and polypropylene resin, polyamide resin, acrylonitrile-butadiene-styrene copolymer resin, acrylic resin, and polyester resins such as polybutylene terephthalate resin. Of these, polypropylene resin is preferred for the core layer 20. When a thermoplastic resin sheet material is used as the material for forming the core layer, the upper wall portion 21 and lower wall portion 22, which are formed at the same time, are also made of the same material.

[0035] The thermoplastic resins constituting the skin layers 30, 40 are preferably the same type of thermoplastic resin as the core layer 20 and the nonwoven fabric layer F. If these thermoplastic resins are each independently a polyolefin resin such as polyethylene resin or polypropylene resin, the skin layer and the nonwoven fabric layer can be more firmly integrated at an appropriate heating temperature, resulting in a stable laminate structure. The resulting pore distribution can be adjusted by adjusting the heating temperature, the melting point of each material, and the strength of pressure applied during bonding. Furthermore, the pores in the skin layer are not filled, as would be the case if an adhesive or the like were used. In addition, a non-thermoplastic resin may be used instead of the thermoplastic resin, or a part of the thermoplastic resin may be a non-thermoplastic resin. The nonwoven fabric layer F is made of one type of resin. This one type of resin includes two cases: a case where the fiber material is made of only one type of resin, and a case where fibers made of multiple types of resin materials are mixed, but only some of the resins melt during welding.

[0036] In addition to the above resins, fibers other than the above resins, such as metal fibers, inorganic fibers, or cellulose fibers, may be contained within a range that does not impair adhesion between the resin and the skin layer, or may not be contained. The core layer may be formed from a cellular sheet made of a porous or foamed material, or may be formed from a sheet that is neither porous nor foamed. The skin layer may be made of a sheet or film having smooth surfaces on both sides. When laminated to the core layer, the outer surface (the surface on which the nonwoven fabric is laminated) does not need to contain resin fibers. If resin fibers are present, the resulting structure may differ from the structure in which the skin layer and nonwoven fabric layer are welded together in the sound-absorbing structure of the present invention.

[0037] (Method of manufacturing sound-absorbing structure) One of the two manufacturing methods for obtaining a sound-absorbing structure of the present invention is a method for manufacturing a hollow board material having a side wall portion extending in a thickness direction to divide cells, and an upper wall portion and a lower wall portion provided at the edge of the side wall portion, in which a plurality of cells having a structure in which a plurality of openings are formed are arranged side by side, the main surface of the hollow board material having the openings being laminated with a skin layer, and a nonwoven fabric layer being laminated with an intermediate layer on the skin layer, the intermediate layer containing a material derived from a portion of the fibers of the nonwoven fabric layer, A. A side wall portion that stands in the thickness direction and divides the cells, and an upper wall portion and a lower wall portion that are provided at the edge of the side wall portion, One of the upper wall portion and the lower wall portion has a structure in which a plurality of openings are formed, and a skin layer is laminated on a main surface of a hollow plate material in which a plurality of cells are arranged side by side, and and / or Only the skin layer side of the nonwoven fabric, heating the B. A step of pressing the surface of the skin layer and the skin layer side of the nonwoven fabric together; in order, This is a method for manufacturing a sound-absorbing structure having a structure in which the skin layer is laminated on the main surface of a hollow board material in which a plurality of cells are arranged side by side, and the nonwoven fabric layer is welded to the surface of the skin layer via the intermediate layer.

[0038] The other of the two methods for producing the sound absorbing structure of the present invention is C. A step of heating only the surface of the skin layer and / or only the skin layer side of the nonwoven fabric; D. A step of pressure-bonding the surface of the skin layer and the skin layer side of the nonwoven fabric to obtain a laminate; E. The skin layer side surface of the obtained laminate; The laminated laminated sheet comprises a side wall portion extending in a thickness direction to partition cells, and an upper wall portion and a lower wall portion provided at an edge of the side wall portion, The hollow plate material has a side wall portion that stands in the thickness direction and divides the cells, and an upper wall portion and a lower wall portion that are provided at the end edge of the side wall portion, and one of the upper wall portion and the lower wall portion has a structure in which a plurality of openings are formed, and the main surface of the hollow plate material in which a plurality of cells are arranged side by side is laminating step; containing This is a method for manufacturing a sound-absorbing structure having a structure in which the skin layer is laminated on the main surface of a hollow board material in which a plurality of cells are arranged side by side, and the nonwoven fabric layer is welded to the surface of the skin layer via the intermediate layer. When laminating these layers, they can be pressure-welded using a roller or a pressure plate as needed. The heating method can be any method that can uniformly heat the heated surface, and any known method can be used.

[0039] (Method of forming intermediate layer) For each of the two methods described above for obtaining intermediate layers having the structures A to C, the following three lamination methods for the nonwoven fabric layer and the skin layer, A to C, can be employed, which correspond particularly to the structures A to C. It is preferable to heat the entire surface of the skin layer and / or nonwoven fabric layer on the side where the intermediate layer is to be formed to form the intermediate layer, in order to obtain an excellent sound absorbing effect. Alternatively, it is also possible to heat a portion of each surface of the skin layer and nonwoven fabric layer on the side where the intermediate layer is to be formed to form the intermediate layer. The intermediate layer in the obtained sound absorbing structure may be formed over the entire surface of the sound absorbing structure, or may be provided on a portion of the surface. It is also possible not to heat the entire nonwoven fabric layer in the thickness direction.

[0040] a. A method in which only the surface of the skin layer is heated in advance to the extent that it melts, and then a nonwoven fabric is pressed onto that surface, so that some of the fibers of the nonwoven fabric are embedded in the skin layer without melting. Figure 2(a) shows a schematic cross-sectional view of the laminated structure of the skin layer and nonwoven fabric layer obtained by this method. In this figure, some of the fibers of the nonwoven fabric are present in the skin layer to form an intermediate layer, and the rest of the nonwoven fabric has the structure of a nonwoven fabric. In this case, it is preferable that the depth to which the fibers are embedded from the surface of the skin layer is 0.1 μm or more.

[0041] b. A method in which only one side of a nonwoven fabric is heated in advance to partially melt it, and one side of the melted nonwoven fabric is pressed against the surface of the skin layer to form an intermediate layer formed by melting the surface fibers of the nonwoven fabric on the surface of the skin layer, and the nonwoven fabric layer is welded to the intermediate layer. Figure 2(b) shows a schematic cross-sectional view of the laminated structure of the skin layer and nonwoven fabric layer obtained by this method. In this figure, a layer formed by melting some of the fibers of the nonwoven fabric exists on top of the skin layer as an intermediate layer, and the rest of the nonwoven fabric has the structure of a nonwoven fabric layer. In this case, the proportion of the area of ​​the skin layer surface where the fibers of the nonwoven fabric are welded is preferably 10% or more.

[0042] (c) A method in which only the surface of the skin layer is heated in advance to the extent that it melts, and if necessary, only one side of the nonwoven fabric is heated in advance to partially melt it, and the molten skin layer surface is pressed against a portion of the fibers of the nonwoven fabric, which may also be melted, so that the fibers of the nonwoven fabric and the resin of the skin layer melt and mix, integrating the two. Figure 2(c) shows a schematic cross-sectional view of the laminate structure of the skin layer and nonwoven fabric layer obtained by this method. In this figure, a portion of the fibers of the nonwoven fabric melts with the resin on the surface of the skin layer, forming an integrated layer that serves as an intermediate layer on the surface of the skin layer, and the rest of the nonwoven fabric has the structure of a nonwoven fabric.

[0043] In either case, the step of forming holes in the skin layer can be performed at any of three stages: before laminating the skin layer on the core layer, after laminating the skin layer on the core layer, or after laminating the nonwoven fabric on the skin layer. In the structure of Figure 1(a), when forming holes 15 in the skin layer by piercing a needle or the like, an opening may be formed in one wall of the core layer at the same time. In this case, the holes 15 and the opening can be formed in a single process. Furthermore, when heating the nonwoven fabric, the nonwoven fabric is not heated so as to melt the entire thickness of the nonwoven fabric. If the entire thickness of the nonwoven fabric is heated above its melting point, it will not have the structure of a nonwoven fabric. Therefore, it is sufficient to heat the entire surface or a portion of at least one of the surfaces of these layers that are stacked opposite each other. However, a method may be adopted in which the needle or other means for forming holes also serves as the heating member, and after the skin layer and the nonwoven fabric are stacked, the holes are opened and both layers are heated and welded at the same time. If this method is used, the area of ​​the part where the resin is melted and welded is small, so it may be difficult to efficiently transmit the vibration of the nonwoven fabric layer to the skin layer.

[0044] (Sound-absorbing structure obtained by method a) The sound-absorbing structure obtained by the above method a has an intermediate layer in the skin layer, which has a structure in which the surface fibers of the nonwoven fabric before lamination are embedded. Even in the sound-absorbing structure obtained by method a, some of the fibers in the intermediate layer may also be melted by the heat of the molten skin layer, resulting in a partially mixed structure (corresponding to an intermediate layer having both the above structures a and c). (Sound-absorbing structure obtained by method b) The sound-absorbing structure obtained by the above method b) has an intermediate layer on the surface of the skin layer, which has a structure formed by fusing the fibers on the surface of the nonwoven fabric before lamination. At this time, a thin layer of melted fibers of the nonwoven fabric is integrally formed on the surface of the skin layer. Even in the sound-absorbing structure obtained by method b), the heat of the molten fibers may cause part of the skin layer to melt, resulting in a partially mixed structure (corresponding to an intermediate layer having both the above structures b and c). (Sound-absorbing structure obtained by method c) The sound absorbing structure obtained by the above method c has an intermediate layer formed by melt-mixing the fibers on the surface of the nonwoven fabric before lamination with the resin of the skin layer.

[0045] (Laminate not included in the sound-absorbing structure of the present invention) The sound absorbing structure of the present invention has the above structure obtained by the above method. Therefore, it does not include laminates in which the layer provided directly on at least one surface of the hollow plate material is a layer of only nonwoven fabric or a layer consisting only of a composition containing resin and nonwoven fabric throughout the entire thickness of the layer. Naturally, this does not include laminates formed by laminating a nonwoven fabric and a substrate, and then heating and compressing the nonwoven fabric on the side opposite the substrate to melt at least some of the components, or laminates having a structure consisting of a substrate and a layer formed by heating the entire thickness of the nonwoven fabric to melt at least some of the components. This does not include a laminate in which some of the fibers on the surface of the nonwoven fabric that are in point contact with the surface of the skin layer are in point contact with the fibers of the skin layer and / or nonwoven fabric that have been melted. It does not include a laminate in which a nonwoven fabric is laminated on the surface of a skin layer via an adhesive layer or pressure-sensitive adhesive layer. The layers provided on at least one surface of the hollow plate material include the skin layer, the intermediate layer, and the nonwoven fabric layer in this order.

[0046] When the laminate of the present invention is installed on the interior surface of the ceiling or door of an automobile, for example, it is used by bending the laminate so as to fit the inner surface shape of the ceiling or door, which is by no means flat. Furthermore, since the present invention involves laminating nonwoven fabric so that it is directly fixed to the skin layer, even if the laminate is bent to form the above-mentioned inner surface shape, the skin layer and nonwoven fabric layer are integrated and do not peel off from each other, so that the sound absorption performance as designed can be achieved regardless of the position on the laminate. In the present invention, the holes formed in the upper and / or lower walls of the hollow board may or may not be partially sealed with a skin layer, and the skin layer and the nonwoven fabric layer are not integrated with a hot melt adhesive. [Example]

[0047] Sample 1 was prepared as follows (corresponding to the case of Patent Document 1). The specimen consists of a core layer, a hollow plate formed from a 0.3 mm thick polypropylene resin sheet with multiple cells arranged side by side, and skin layers of 0.3 mm thick polypropylene resin sheets bonded to both sides of the core layer, for a total plate thickness of 20 mm. The pitch between the centers of adjacent cells is 10.0 mm (average pitch P1 = 10.0 mm). One side of the specimen (the closed wall) has through holes with a diameter of approximately 1.2 mm that connect the inside and outside of the cell. The spacing between adjacent through holes in the direction in which the cells are arranged side by side is 8.0 mm (spacing P2 = 8.0 mm). The opening edges of the through holes formed in the closed wall of the cell are located in the internal space of the cell.

[0048] The above sample 1 is placed in a container with dimensions of 910 x 1820 mm (1.66 m 2 ) and cut to a volume of 24.82 m 3The reverberation room sound absorption coefficient was measured in a reverberation room of 315Hz, 400Hz, 500Hz, 630Hz, 800Hz, 1000Hz, 1250Hz, 1600Hz, 2000Hz, 2500Hz, 3150Hz, 4000Hz, and 5000Hz, and the results are shown in Table 1. All conditions other than the length and width of the specimen and the volume of the reverberation room were determined in accordance with the JIS A1409 method for measuring reverberation room sound absorption coefficient.

[0049] Sample 2 (corresponding to intermediate layer A of the present invention) was prepared as follows. After heating the surface of the skin layer of Sample 1 to melt it slightly, a solid polyester nonwoven fabric (3.0 mm thick) was quickly laminated on top of it, burying the fiber ends of the polyester nonwoven fabric on the surface of the skin layer to form an integrated intermediate layer. The reverberation chamber sound absorption coefficient was measured in the same manner as Sample 1, and the results are shown in Table 1.

[0050] Sample 3 (corresponding to intermediate layer A in the present invention) was prepared as follows. A solid polypropylene nonwoven fabric (3.0 mm thick) with only one surface melted was attached to the unheated surface of the skin layer of Sample 1, and an intermediate layer (I) formed from the fiber ends of the polypropylene nonwoven fabric and the nonwoven fabric layer connected to the intermediate layer were integrated on the surface of the skin layer. The reverberation chamber sound absorption coefficient was measured in the same manner as Sample 1, and the results are shown in Table 1.

[0051] Sample 4 (corresponding to intermediate layer C of the present invention) was prepared as follows. After heating the above sample 1 so that only the surface of the skin layer was slightly melted, a solid polypropylene nonwoven fabric (3.0 mm thick) was quickly laminated onto it, and the melted skin layer surface and the skin layer side surface of the polypropylene nonwoven fabric were melted and integrated to form intermediate layer C. On the outside of intermediate layer C, there was a nonwoven fabric layer consisting of a layer that was not on the skin layer side of the polypropylene nonwoven fabric. The reverberation chamber sound absorption coefficient was measured in the same manner as for sample 1, and the results are shown in Table 1.

[0052] Sample 5 was prepared as follows. A solid polypropylene nonwoven fabric (thickness 3.0 mm) was laminated with a polyolefin hot melt adhesive onto the surface of the skin layer of Sample 1. The reverberation chamber sound absorption coefficient was measured in the same manner as Sample 1, and the results are shown in Table 1.

[0053] Table 1 shows that Sample 1 exhibits reasonable sound absorption performance in the frequency band of 630 to 1600 Hz. In particular, in the frequency band of 800 to 1000 Hz, which includes human voices, it exhibited a high reverberation chamber sound absorption coefficient of 0.8 or more. However, the sound absorption coefficient decreases as the frequency increases.

[0054] [Table 1]

[0055] Sample 1, which does not have a nonwoven fabric layer, does not achieve a sufficient sound absorption coefficient, especially in the high frequency range. Similarly, Sample 5, in which the nonwoven fabric is bonded to the skin layer with an adhesive, also does not achieve a sufficient sound absorption coefficient in the high frequency range. The same results are obtained even when the nonwoven fabric is heat-sealed to the skin layer so as to make point contact (i.e., when no specific intermediate layer is provided). In contrast to these, Samples 2, 3, and 4, which are examples in accordance with the present invention, were able to obtain high sound absorption coefficients even at frequencies of 1600 Hz and 2000 Hz, and in addition, were able to achieve even higher sound absorption coefficients in the frequency range of 2500 Hz or higher. As a result, according to the present invention, high sound absorption coefficients can be achieved in a wider frequency range, including the ranges of 600 Hz and 2000 Hz. In other words, the present invention does not simply involve heat-sealing a nonwoven fabric to the surface of the skin layer, but rather by selecting to form an intermediate layer in a specific form, it exhibits significant effects compared to cases where this is not the case. [Industrial Applicability]

[0056] The sound absorbing structure of the present invention can be installed in any application requiring sound absorption, such as the interior of an automobile or the interior wall of a building. [Explanation of symbols]

[0057] S...cell, S1...first cell, S2...second cell, 10...sound absorbing structure, 15...hole, 15a...first hole, 20...core layer (hollow plate material), 21...upper wall portion, 22...lower wall portion, 23...side wall portion, 30...skin layer, 40...skin layer

Claims

1. The hollow plate material has a side wall portion that stands in the thickness direction and divides the cells, and an upper wall portion and a lower wall portion that are provided at the edge of the side wall portion, and one of the upper wall portion and the lower wall portion has a structure in which a plurality of openings are formed, and a skin layer made of a film-like material and having smooth surfaces on both sides is laminated on the main surface of the hollow plate material in which a plurality of cells are arranged side by side, and the surface of the skin layer and a resin are laminated on the main surface of the hollow plate material. ３ and a nonwoven fabric layer having a thickness of 0.5 to 20.0 mm, which has one or more of the structures A to C below, and which is welded to the skin layer via an intermediate layer so that the nonwoven fabric layer does not come into point contact with the skin layer. A: An intermediate layer formed by embedding some of the fibers of the nonwoven fabric layer in the skin layer while maintaining their fiber shape. A: An intermediate layer having a structure in which some fibers of the nonwoven fabric layer are once melted and adhered to the surface of the skin layer. C: An intermediate layer having a structure in which the surface of the skin layer and some of the fibers of the nonwoven fabric layer are once melted and mixed together.

2. The sound absorbing structure according to claim 1, wherein the skin layer has a plurality of holes formed therein.

3. The sound-absorbing structure according to claim 2, wherein, in the inner diameter distribution of holes on the surface of the skin layer provided on the one wall portion facing the nonwoven fabric layer, when the average inner diameter is set to 100, 30% to 70% of the total number of holes have inner diameters that are 80% to 120% of the average inner diameter.

4. A. The cell structure includes a side wall portion extending in the thickness direction to define a cell, and an upper wall portion and a lower wall portion provided at the edge of the side wall portion, a skin layer surface formed by laminating a skin layer made of a film-like material having smooth surfaces on both sides on a main surface of a hollow plate material having a structure in which a plurality of openings are formed in one of the upper wall portion and the lower wall portion and a plurality of cells are arranged side by side; and / or the skin layer side of the nonwoven fabric layer made of resin fibers; heating the B. A step of pressing the surface of the skin layer and the skin layer side of the nonwoven fabric layer together; in order, The skin layer is laminated on the main surface of a hollow plate material in which a plurality of cells are arranged side by side, and the surface of the skin layer and a resin are laminated on the main surface of the hollow plate material. ３ and a nonwoven fabric layer having a thickness of 0.5 to 20.0 mm, which has one or more of the structures A to C below, and is welded to the skin layer via an intermediate layer so that the nonwoven fabric layer is not in point contact with the skin layer. A: An intermediate layer in which some of the fibers of the nonwoven fabric layer are embedded in the skin layer while maintaining their fiber shape. A: An intermediate layer having a structure in which some of the fibers of the nonwoven fabric layer are once melted and adhered to the surface of the skin layer. C: An intermediate layer having a structure in which the surface of the skin layer and some of the fibers of the nonwoven fabric layer are once melted and mixed together.

5. C. A step of heating the surface of the skin layer made of a film-like material having smooth surfaces on both sides and / or the skin layer side of the nonwoven fabric layer made of resin fibers; D. A step of pressure-bonding the surface of the skin layer and the skin layer side of the nonwoven fabric layer to obtain a laminate having one or more of the following structures A to C via an intermediate layer, in which the nonwoven fabric layer is not in point contact with the skin layer: E. the skin layer side surface of the obtained laminate; The laminated laminated sheet comprises a side wall portion extending in a thickness direction to partition cells, and an upper wall portion and a lower wall portion provided at the edge of the side wall portion, The hollow plate material has a side wall portion that stands in the thickness direction and divides the cells, and an upper wall portion and a lower wall portion that are provided at the edge of the side wall portion, and one of the upper wall portion and the lower wall portion has a structure in which a plurality of openings are formed, and the main surface of the hollow plate material in which a plurality of cells are arranged side by side is laminating step; containing The skin layer is laminated on the main surface of a hollow plate material in which a plurality of cells are arranged side by side, and the surface of the skin layer is made of resin fibers, and the density is 5 to 200 mg / cm ３ A method for manufacturing a sound-absorbing structure having a structure in which a nonwoven fabric layer having a thickness of 0.5 to 20.0 mm is welded. A: An intermediate layer in which some of the fibers of the nonwoven fabric layer are embedded in the skin layer while maintaining their fiber shape. A: An intermediate layer having a structure in which some of the fibers of the nonwoven fabric layer are once melted and adhered to the surface of the skin layer. C: An intermediate layer having a structure in which the surface of the skin layer and some of the fibers of the nonwoven fabric layer are once melted and mixed together.

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