Sound absorbing material, and manufacturing method of sound absorbing material

Abstract

To improve sound absorbing performance.SOLUTION: A sound absorbing material of the present invention absorbs sound from a component. The sound absorbing material 1 comprises a rising part 4 rising from a mounting part P at which the sound absorbing material 1 is mounted, and an opposing part 5 facing the component in the side opposite to the mounting part P of the rising part 4. Each of the rising part 4 and the opposing part 5 includes a core layer 11 and a ventilation resistance layer 12. In at least a part of the opposing part 5 and the rising part 4, variation in thickness T of the ventilation resistance layer 12 is 40% or less of an average value of the thickness T of the ventilation resistance layer 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to sound absorbing materials and methods of making sound absorbing materials. [Background technology]

[0002] Various types of sound-absorbing materials are known for suppressing noise and the like. Patent Document 1 describes a laminated sound-absorbing member. The laminated sound-absorbing member includes a sound-absorbing material and an airflow resistance film bonded to the surface of the sound-absorbing material. The airflow resistance film is located closer to the sound source than the sound-absorbing material. The airflow resistance film is made of a mixture of meltblown fibers with a fiber diameter of 10 μm or less and binder fibers, and has a weight per unit area of ​​50 to 250 g / m. 2 The web is heated and pressurized, and the solidity is adjusted to 10% or more.

[0003] Patent Document 2 describes an automobile silencer that is press-molded and has first and second molded surfaces that are opposite to each other in the thickness direction. The automobile silencer has at least a first fiber layer on which the first molded surface is formed, and a second fiber layer that is integrated with the surface of the first fiber layer opposite to the first molded surface and has fibers partially present therein. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-57663 A [Patent Document 2] JP 2016-155461 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, some of the sound sources that generate noise, such as vehicle parts, have complex structures. When applying a sound-absorbing material to such objects, the shape of the sound-absorbing material may be three-dimensional. That is, the sound-absorbing material may have a 3D shape having a surface that is approximately parallel to the surface on which the sound-absorbing material is arranged and a surface that faces in a direction intersecting the surface on which the sound-absorbing material is arranged. When a 3D-shaped sound-absorbing material is provided with the above-mentioned air-permeability resistance film, the thickness of the air-permeability resistance film may vary during molding. Therefore, there is room for improvement in terms of sound-absorbing performance. [Means for solving the problem]

[0006] A sound-absorbing material according to one embodiment of the present disclosure is a sound-absorbing material that absorbs sound from a component, and includes a rising portion that rises from an attachment portion to which the sound-absorbing material is attached, and an opposing portion that faces the component on the opposite side of the rising portion from the attachment portion, each of the rising portion and the opposing portion including a core layer and an air-permeability resistance layer, and in at least a portion of the opposing portion and the rising portion, the variation in thickness of the air-permeability resistance layer is 40% or less of the average thickness of the air-permeability resistance layer.

[0007] This type of sound absorbing material includes a rising portion rising from the mounting portion and a facing portion facing the component. Therefore, the shape of the sound absorbing material is three-dimensional, so it can be used for components having complex shapes. Each of the rising portion and the facing portion includes a core layer and an airflow resistance layer. Therefore, the sound absorbing performance can be improved by absorbing sound with the core layer while appropriately suppressing airflow with the airflow resistance layer. And, in at least a part of the material, the variation in thickness of the airflow resistance layer is 40% or less of the average thickness. In this case, the variation in thickness of at least a part of the airflow resistance layer is constant, so that the sound absorption coefficient of the airflow resistance layer can be increased. Therefore, the sound absorbing performance can be improved.

[0008] In another embodiment of the sound-absorbing material, the variation in thickness of the air resistance layer may be 40% or less of the average value in 80% or more of the area of ​​the sound-absorbing material, including the opposing portion and the rising portion but excluding the edge portion.

[0009] In a sound-absorbing material according to another embodiment, the air flow resistance layer may have a thickness of 1 mm or more and 6 mm or less.

[0010] In a sound-absorbing material according to another embodiment, the airflow resistance value of the airflow resistance layer may be within a range of a reference value ±120 Rayls.

[0011] In a sound-absorbing material according to another embodiment, the airflow resistance value of the airflow resistance layer may be 300 Rayls or more and 1100 Rayls or less.

[0012] In a sound-absorbing material according to another embodiment, the airflow resistance layer may be located on the component side as viewed from the core layer.

[0013] In a sound-absorbing material according to another embodiment, at least one of the air flow resistance layer and the core layer may contain microfibers.

[0014] A manufacturing method for a sound-absorbing material according to one embodiment of the present disclosure is a manufacturing method for a sound-absorbing material having a core layer and an air permeability layer, and includes the steps of preparing a material constituting the air permeability layer, sandwiching the material constituting the air permeability layer in a first mold to form the air permeability layer, and sandwiching the material constituting the core layer between the air permeability layer and a second mold to form the core layer.

[0015] In this type of manufacturing method for a sound-absorbing material, first, the material for the airflow resistance layer is sandwiched between a first mold to form the airflow resistance layer. Therefore, by first forming the airflow resistance layer by sandwiching it between the first mold, the thickness of the airflow resistance layer can be made constant using the first mold. After that, the core layer is formed in the second mold on the airflow resistance layer whose thickness has been made constant. Therefore, a sound-absorbing material having high sound-absorbing performance and including an airflow resistance layer and a core layer whose thicknesses are constant can be manufactured.

[0016] The step of forming the airflow resistance layer may include a step of adjusting the thickness of the airflow resistance layer by pressing, or by using a calendar roll and a press. Effect of the Invention

[0017] According to the present disclosure, sound absorbing performance can be improved. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a perspective view showing an example of a sound-absorbing material according to an embodiment. [Diagram 2] FIG. 4 is a cross-sectional view showing another example of a sound-absorbing material according to an embodiment. [Diagram 3] 1A to 1C are diagrams illustrating an exemplary procedure for a method for manufacturing a sound-absorbing material according to an embodiment. [Figure 4] FIG. 4 is a diagram showing a continuation of the procedure in FIG. [Diagram 5] FIG. 5 is a diagram showing a continuation of the procedure in FIG. 4. [Figure 6] FIG. 6 is a diagram showing a continuation of the procedure in FIG. 5. [Figure 7] FIG. 7 is a diagram showing a continuation of the procedure in FIG. 6. [Figure 8] FIG. 8 is a diagram showing a continuation of the procedure in FIG. 7. [Figure 9] 1 is a graph showing experimental results of sound absorption coefficient in an exemplary sound absorbing material. [Figure 10] 1 is a graph showing experimental results of sound absorption coefficient in an exemplary sound absorbing material. [Figure 11] 1 is a graph showing experimental results of sound absorption coefficient in an exemplary sound absorbing material. [Figure 12] 1 is a graph showing the relationship between sound frequency and sound absorption coefficient for each thickness of the air flow resistance layer. [Figure 13] 1 is a graph showing experimental results of the sound absorption coefficient of the sound-absorbing materials according to the examples and the comparative examples. [Figure 14] 1 is a graph showing experimental results of the sound absorption coefficient of the sound-absorbing materials according to the examples and the comparative examples. [Figure 15] 1A and 1B are diagrams showing cross sections of sound-absorbing materials in a comparative example and an example, respectively. [Figure 16] 1A and 1B are diagrams showing cross sections of sound-absorbing materials in a comparative example and an example, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the sound-absorbing material and the manufacturing method of the sound-absorbing material according to the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiment, but is intended to include all modifications within the scope of the claims and equivalents thereto. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicated descriptions are omitted as appropriate. In addition, the drawings may be partially simplified or exaggerated for ease of understanding, and the dimensional ratios and the like are not limited to those shown in the drawings.

[0020] The sound-absorbing material according to the embodiment absorbs sound from a part. In the embodiment, the "part" refers to a part that generates sound and is a target for sound absorption. For example, the "part" may be a mechanical part, an automobile part, an electric part, or an electronic part, and the type of the "part" is not limited. As a further specific example, the "part" may be an automobile component, an airplane, or a building substrate.

[0021] The sound-absorbing material has a rising portion that rises from an attachment portion to which the sound-absorbing material is attached. The "attachment portion" refers to the portion to which the sound-absorbing material is attached. The "rising portion" refers to a portion that rises from the attachment portion and has a surface that intersects with the attachment portion. The sound-absorbing material has a facing portion that faces the part on the opposite side of the rising portion from the attachment portion. For example, the "facing portion" refers to the top surface portion of the sound-absorbing material that has an uneven shape.

[0022] Further examples of objects to which the sound absorbing material may be attached include door panels, aircraft frames, in-wall insulation, integrated ducts, transportation equipment (aircraft, rotorcraft, or trains), electronic equipment (televisions, computers, or servers), storage devices, power supplies, air conditioning systems, upholstery, personal protective equipment, clothing, blankets, and any of the furniture. Examples of locations where the sound absorbing material may be attached may be elements around these structural examples, such as carpeting or trunk liners.

[0023] Additionally, sound absorbing materials may be installed in fender liners, dashboard fronts, floor systems, wall panels, duct insulation, liners, headliners, aircraft panels, drapes, ceiling tiles, or further applications thereof. Sound absorbing materials may be similar to filtration media, surgical drapes, wipes, and liquid and gas filters.

[0024] FIG. 1 is a perspective view showing an exemplary sound-absorbing material 1. As shown in FIG. 1, the sound-absorbing material 1 absorbs sound from a part. As an example, the sound-absorbing material 1 may be a molded panel. For example, the sound-absorbing material 1 is arranged so as to cover the part, and absorbs sound from the part while covering the part. As an example, the shape of the sound-absorbing material 1 is a pentagon having five corners C. However, the shape of the sound-absorbing material 1 may be a polygonal shape such as a triangular shape, a rectangular shape, or a hexagonal shape, or a circular shape or an elliptical shape, and is not particularly limited.

[0025] For example, the sound-absorbing material 1 may be a sound-absorbing material provided for noise suppression inside an automobile or for noise suppression outside an automobile. Also, the part to be subjected to noise suppression may be a vehicle part, and the sound-absorbing material 1 may be disposed in an engine room of the vehicle. However, the sound-absorbing material 1 is not limited to being used in automobiles, and can be used in various things and for various purposes.

[0026] The exemplary sound-absorbing material 1 has an uneven shape (three-dimensional shape, 3D shape) with an edge 2 facing the mounting part P and a protrusion 3 protruding from the edge 2. In this way, since the sound-absorbing material 1 has an uneven shape, it is possible for the sound-absorbing material 1 to reliably cover even parts having complex shapes by conforming to the shape of the parts. As an example, the sound-absorbing material 1 is placed in a gap formed inside the engine room.

[0027] For example, the edge portion 2 includes a pair of first sides 2b extending in a first direction D1 that is a direction along the mounting portion P, and a pair of second sides 2c extending in a second direction D2 that is a direction along the mounting portion P and intersects with the first direction D1. For example, one first side 2b and one second side 2c are each shorter than the other first side 2b and the other second side 2c, respectively, and the sound-absorbing material 1 further has an inclined side 2d extending from the one second side 2c toward the one first side 2b. However, the shape of the edge portion 2 is not limited to the above example.

[0028] For example, the edge portion 2 is formed with a hole portion 2f through which a fixing means for fixing the sound absorbing material 1 to the part is inserted. The hole portion 2f penetrates in a third direction D3 intersecting both the first direction D1 and the second direction D2. The third direction D3 corresponds to a direction in which the sound absorbing material 1 protrudes or recesses with respect to the part, and may be, for example, an out-of-plane direction of the mounting portion P. As an example, the edge portion 2 may have a plurality of holes 2f, and at least some of the plurality of holes 2f may be formed at the corners C of the sound absorbing material 1. In the example of FIG. 1, the hole portion 2f is formed at both ends of each first side 2b and at a middle portion of the longer first side 2b of the pair of first sides 2b.

[0029] The protruding portion 3 includes a first protruding portion 3b protruding from the edge portion 2 and a second protruding portion 3c protruding further from the first protruding portion 3b. The sound absorbing material 1 may have a recess (concave portion) in at least one of the regions of the first protruding portion 3b and the second protruding portion 3c. In the portions of the first protruding portion 3b and the second protruding portion 3c facing the hole portion 2f, a concave portion 3d is formed that is recessed along the circumferential direction of the hole portion 2f. As an example, the first protruding portion 3b is formed around one corner C of the sound absorbing material 1. The first protruding portion 3b may be formed on the portion of the corner C side of the longer first side 2b of the pair of first sides 2b and on the portion of the shorter second side 2c of the pair of second sides 2c. However, the shape of the sound absorbing material 1 is not limited to the above example and can be changed as appropriate.

[0030] Fig. 2 is a cross-sectional view showing a more simplified example of the sound-absorbing material 1. As described above, the sound-absorbing material 1 includes an edge portion 2, a first protruding portion 3b, and a second protruding portion 3c. Each of the first protruding portion 3b and the second protruding portion 3c includes a rising portion 4 rising from the edge portion 2 in the third direction D3, and a facing portion 5 extending from the top of the rising portion 4 in the first direction D1 and the second direction D2 and facing the component. The component is provided on the mounting portion P side of the facing portion 5 in the third direction D3 (the lower side in Fig. 2).

[0031] Each of the rising portion 4 and the facing portion 5 includes, for example, a core layer 11, an airflow resistance layer 12, a first cover layer 13, a second cover layer 14, and a thin plate layer 15. The exemplary thin plate layer 15 is a layer formed by crushing the core layer 11, the airflow resistance layer 12, the first cover layer 13, and the second cover layer 14 at the edge portion 2. In this manner, the sound-absorbing material 1 having the airflow resistance layer 12 is formed into a 3D shape.

[0032] The sound-absorbing material 1 is a sound-absorbing material formed into a 3D shape, and the variation in thickness T of the airflow resistance layer 12 at any location is within ±40% of the average value of the thickness T. That is, in at least a part of the rising portion 4 and the facing portion 5, the variation in thickness T of the airflow resistance layer 12 is 40% or less of the average value of the thickness T. For example, in 80% or more of the area of ​​the sound-absorbing material 1 that includes the rising portion 4 and the facing portion 5 but does not include the edge portion 2, the variation in thickness T of the airflow resistance layer 12 may be 40% or less of the average value. Note that FIG. 2 shows an example in which the thickness T of the airflow resistance layer 12 is constant in areas other than the part corresponding to the thin plate layer 15 of the sound-absorbing material 1.

[0033] In the embodiment, as described above, the variation in the thickness T of the airflow resistance layer 12 is suppressed. The variation in the thickness T of the airflow resistance layer 12 may be 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 5% or less, 3% or less, 2% or less, or 1% or less of the average value of the thickness T. In addition, the variation in the thickness T of the airflow resistance layer 12 may be 40% or less of the average value in 85% or more, 90% or more, 95% or more, 97% or more, 98% or more, or 99% or more of the region of the sound-absorbing material 1 that includes the rising portion 4 and the facing portion 5 but does not include the edge portion 2.

[0034] The thickness T of the air permeability resistance layer 12 is, for example, 1 mm or more and 6 mm or less. The air permeability resistance value of the air permeability resistance layer 12 is, for example, within a range of a reference value ±120 Rayls. The "reference value" is a reference air permeability resistance value of the air permeability resistance layer adjusted to exhibit a desired sound absorption performance, and may be determined according to the thickness of the core layer 11. The "reference value" may be a value determined in advance by an experiment, or may be a value determined by a simulation.

[0035] The air permeability of the air permeability layer 12 may be 300 Rayls or more and 1100 Rayls or less. However, the thickness T of the air permeability layer 12 and the air permeability of the air permeability layer 12 can be changed as appropriate, as described below. The thickness T of the air permeability layer 12 and the air permeability of the air permeability layer 12 may be determined according to the core layer 11 (for example, the thickness of the core layer 11, etc.).

[0036] The materials of the first cover layer 13 and the second cover layer 14 are not particularly limited. As an example, the first cover layer 13 is made of a spunbond nonwoven fabric, and the second cover layer 14 is made of an SMS nonwoven fabric. The first cover layer 13 and the second cover layer 14 are provided to cover the core layer 11 and the air resistance layer 12. As an example, the first cover layer 13 is black in color, and the second cover layer 14 is white in color.

[0037] It is also possible to omit at least one of the first cover layer 13, the second cover layer 14, and the thin plate layer 15. For example, instead of at least one of the first cover layer 13 and the second cover layer 14, a film separate from the first cover layer 13 and the second cover layer 14 may be formed by spraying at least one of the core layer 11 and the air permeability layer 12. For example, in terms of thickness in the third direction D3, the core layer 11 is the thickest, the air permeability layer 12 is the second thickest, and the first cover layer 13 and the second cover layer 14 are the thinnest.

[0038] The sound absorbing material 1 including the core layer 11 and the airflow resistance layer 12 exhibits high sound absorbing properties, for example, in a frequency band of 100 Hz or more and 3000 Hz or less. For example, the airflow resistance layer 12 may be a layer that enhances the sound absorbing properties of the core layer 11 by bonding to one surface of the core layer 11. As an example, the airflow resistance layer 12 is bonded to the side of the component that is the sound source as viewed from the core layer 11, i.e., the surface of the core layer 11 on the component side (sound source side).

[0039] The type of the core layer 11 is not particularly limited, and various sound-absorbing materials can be used as the core layer 11. For example, the core layer 11 may be a nonwoven fabric, a felt material, a urethane foam material, a microfiber, or a combination thereof. An exemplary core layer 11 may include at least one of melt-blown fiber, staple fiber, and binder fiber. The core layer 11 may be a sound-absorbing material having a lower air resistance than the air resistance layer 12. The thickness of the core layer 11 is not particularly limited, and is determined, for example, by the constraints of the space in which the sound-absorbing material 1 is installed. As an example, the thickness of the core layer 11 is several mm or more and several tens of mm or less.

[0040] The airflow resistance layer 12 is made of, for example, melt-blown microfibers. Both the core layer 11 and the airflow resistance layer 12 may be made of melt-blown microfibers, or only one of them may be made of melt-blown microfibers. The airflow resistance layer 12 may be made of nanofibers produced by electrospinning. However, as described above, when the airflow resistance layer 12 includes melt-blown microfibers, this contributes to improving the performance and reducing the weight of the sound-absorbing material 1.

[0041] The exemplary airflow resistant layer 12 may include meltblown fibers, staple fibers, and / or binder fibers. The binder fibers may be dispersed in the meltblown fibers or may be at least partially melt-bonded by the meltblown fibers. The binder fibers may function as a binder by being at least partially melt-bonded to the high melting point meltblown fibers.

[0042] The melt-blown fibers of the air permeability layer 12 may be made of a resin having a higher melting point than the melt-bonded portion of the binder fiber, and may be made of a fibrous material produced by the melt-blowing method. The melt-blowing method is a method in which a resin raw material is melted and a high-temperature air current is blown onto the fibrous resin extruded from a nozzle to process the fibers into a finer diameter.

[0043] The airflow resistance layer 12 has the function of improving the sound absorbing characteristics of the sound absorbing material 1 by increasing the airflow resistance of the sound absorbing material 1. For example, the airflow resistance layer 12 is a thin-film acoustic member. As an example, the airflow resistance layer 12 has melt-blown fibers with a fiber diameter of 10 μm or less, binder fibers dispersed in the melt-blown fibers and at least a portion of which is melt-bonded to the melt-blown fibers, and staple fibers.

[0044] The staple fiber may be made of any of polyester, polyamide, acrylic, polypropylene, and polyethylene, but is preferably made of polyester fiber in terms of weather resistance, flame retardancy, and recyclability. The staple fiber has a fiber thickness of, for example, 1 denier or more and 100 denier or less.

[0045] The staple fibers are preferably thicker in terms of processability and handling, and are preferably 3 denier or more and 50 denier or less, particularly in consideration of improving productivity with a fiber spreader. From the standpoint of sound absorption, the staple fibers are preferably thinner, and in order to improve sound absorption in the low frequency range of 200 to 1500 Hz, a thin fiber of 15 denier or less is preferred.

[0046] From the viewpoint of processability and handling, the fiber length of the staple fiber is preferably 30 mm or more and 100 mm or less. The cross-sectional shape of the staple fiber may be any of irregular cross-sections such as a circular shape, a T-shape, and a flat shape, and may be a hollow fiber. The staple fiber may be a fiber having crimps, and the crimp state may be, for example, any of a wavy shape, a spiral type, and a combination of a wavy type and a spiral type. If the number of crimps is too small, elasticity and hardness may be insufficient, and if the number of crimps is too large, processing problems may occur. For example, those having 5 to 200 crimps / 25 mm, more preferably 10 to 50 crimps / 25 mm are used.

[0047] As the binder fiber contained in the airflow resistance layer 12, a fiber having a melting point lower than the melting point of the high melting point meltblown fiber at least in a part of the surface can be used. For example, a binder having a melting point of the low melting point portion lower than the melting point of the meltblown fiber by 10°C or more (or 20°C or more) can be used. For example, low melting point polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), etc. can be used as the low melting point portion of the binder fiber. For example, when polybutylene terephthalate (PBT) having a melting point of about 220°C is used as the meltblown fiber, or when polypropylene having a melting point of about 160°C is used as the meltblown fiber, low melting point polyethylene terephthalate (PET) having a melting point of 110°C on the surface can be used as the binder fiber. Note that when used as a sound absorbing material for vehicles, the melting point of the binder fiber may be 90°C or more, 100°C or more, or 120°C or more in order to withstand environmental resistance tests.

[0048] The binder fiber may be fibrous, and the cross-sectional diameter and length of the binder fiber are not particularly limited. From the viewpoint of increasing dispersibility, the binder fiber may be short fiber. As the binder fiber, a staple fiber having a fiber length of 10 mm or more and 100 mm or less, which is manufactured by cutting spun fibers, can be used. Since the contact density with the melt-blown fiber is high at least in a part of the fibrous binder, efficient melt adhesion between the fibers is possible, and the amount of binder fiber required can be reduced. The binder fiber does not have to be a material having a uniform melting point as a whole, and may have a low melting point layer at least on the surface. For example, it may be a fiber having a core-sheath structure, and only the sheath part may have a low melting point. When a fiber having such a core-sheath structure is used, when it is mixed with the melt-blown fiber, only the low melting point binder in the sheath part melts, and the core part remains as a fiber together with the melt-blown fiber, making it possible to improve the air resistance without impairing the properties of the melt-blown fiber.

[0049] In addition, the partially meltable binder fiber bonds the melt-blown fibers together when melted, thereby increasing the airflow resistance of the melt-blown fibers. In addition, the melt-blown fiber structure can be fixed, which increases the stability of the airflow resistance properties and makes handling easier.

[0050] An exemplary airflow resistant layer 12 is a three-component blend of meltblown fibers, staple fibers, and binder fibers, with a weight per unit area of ​​50 g / m 2 Above 250g / m 2 The air-resistance layer 12 is made from a web that satisfies the following criteria. As an example, the solidity of the air-resistance layer 12 is 10% or more. "Solidity" is a value (percentage) obtained by dividing the bulk density of the web by the density of the material that constitutes the web. "Solidity" can be an index of the packing property, air tightness, and breathability within the web.

[0051] The airflow-resistive layer 12 may comprise a polymeric nonwoven layer, which may be made by a meltblowing process. A meltblown nonwoven fibrous layer may contain very fine fibers, in which a thermoplastic polymer stream is extruded through an orifice in a die and attenuated by a converging stream of hot air to form fine fibers. The airflow-resistive layer 12 may be constructed by melt spinning, in which the nonwoven fibers may be extruded as a series of filaments, which are cooled and solidified to form fibers.

[0052] The fibers produced by the melt spinning may be spunbonded. A web containing a set of melt spun fibers is collected as a fibrous web. The airflow resistant layer 12 may include melt spun fibers. The resins constituting these fibers may include, for example, polyolefins such as polypropylene or polyethylene, polyesters, polyethylene terephthalate, polybutylene terephthalate, polyamides, polyurethanes, polybutenes, polylactic acid, polyphenylene sulfide, polysulfones, liquid crystal polymers, polyethylene-covinyl acetate, polyacrylonitrile, cyclic polyolefins, or copolymers or mixtures thereof. The airflow resistant layer 12 may be made of a thermoplastic semi-crystalline polymer. Thermoplastic semi-crystalline polymers include semi-crystalline polyesters or aliphatic polyesters.

[0053] The molecular weight of the aliphatic polyester is not particularly limited. The molecular weight may be, for example, 15,000 (g / mol) or more and 6,000,000 g / mol or less, 20,000 (g / mol) or more and 2,000,000 g / mol or less, or 40,000 (g / mol) or more and 1,000,000 g / mol or less. The molecular weight may be 25 (g / mol) or more. Further, the molecular weight is 15,000 (g / mol), 20,000 (g / mol), 25,000 (g / mol), 30,000 (g / mol), 35,000 (g / mol), 40,000 (g / mol), 45,000 (g / mol), 50,000 (g / mol), 60,000 (g / mol), 70,000 (g / mol), 80,000 (g / mol), 90,000 (g / mol). , 100,000 (g / mol), 200,000 (g / mol), 500,000 (g / mol), 700,000 (g / mol), 1,000,000 (g / mol), 2,000,000 (g / mol), 3,000,000 (g / mol), 4,000,000 (g / mol), 5,000,000 (g / mol), and 6,000,000 (g / mol).

[0054] The airflow resistance layer 12 may include a nonwoven fiber layer, and the diameter of the fibers of the nonwoven fiber layer is not particularly limited. The diameter may be, for example, 0.1 μm or more and 10 μm or less, 0.3 μm or more and 6 μm or less, or 0.3 μm or more and 3 μm or less. The diameter may be less than 0.1 μm. Furthermore, the diameter may be 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 1 ... The thickness may be any of 0 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 22 μm, 25 μm, 27 μm, 30 μm, 32 μm, 35 μm, 37 μm, 40 μm, 42 μm, 45 μm, 47 μm, 50 μm, 53 μm, 55 μm, 57 μm, and 60 μm.

[0055] The air permeability layer 12 may have a porous polymer (may be a porous layer). That is, the air permeability layer 12 may be a layer having a large number of fine pores formed therein. The air permeability layer 12 may be a perforated film or an open-cell foam. When the air permeability layer 12 has fine pores, the average diameter of the pores may be 10 μm or more and 5000 μm or less. The average diameter of the holes may be any of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 150 μm, 170 μm, 200 μm, 300 μm, 350 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 1500 μm, 2000 μm, 3000 μm, 4000 μm, and 5000 μm. The shape of the holes is not limited to a circle, and may be a polygon or an oval.

[0056] When the airflow resistance layer 12 has holes, the porosity of the airflow resistance layer 12 may be, for example, 0.1% or more and 80% or less, 0.2% or more and 70% or less, or 0.5% or more and 60% or less. The porosity of the airflow resistance layer 12 may be any of 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 80%.

[0057] The flexural modulus of the airflow resistance layer 12 may be, for example, 0.2 GPa or more and 10 GPa or less, 0.2 GPa or more and 7 GPa or less, or 0.2 GPa or more and 4 GPa or less. Furthermore, the flexural modulus of the air permeability layer 12 may be any of 0.3 GPa, 0.4 GPa, 0.5 GPa, 0.6 GPa, 0.7 GPa, 1 GPa, 2 GPa, 3 GPa, 4 GPa, 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, 12 GPa, 15 GPa, 17 GPa, 20 GPa, 25 GPa, 30 GPa, 35 GPa, 40 GPa, 50 GPa, 60 GPa, 70 GPa, 80 GPa, 90 GPa, 100 GPa, 120 GPa, 140 GPa, 160 GPa, 180 GPa, 200 GPa, and 210 GPa.

[0058] A polymer may be added to impart flexural elasticity to the airflow-resistant layer 12. The polymer may include, for example, polyolefins, polyesters, fluoropolymers, polylactic acid, polyphenylene sulfide, polyacrylates, polyvinyl chloride, polycarbonates, polyurethanes, and / or blends thereof.

[0059] The airflow resistance layer 12 may be made of fiberglass. The airflow resistance layer 12 may constitute a Helmholtz resonator. The airflow resistance layer 12 contains at least one of organic particles and inorganic particles, which provides excellent sound absorption over a wide frequency range. The porous layer of the airflow resistance layer 12 may contain at least one of organic particles and inorganic particles. In this case, synergistic sound absorption can be achieved.

[0060] The air permeability layer 12 may include at least one of a polymer composition and an inorganic composition. The air permeability layer 12 may be in the form of a film. The air permeability layer 12 may have through holes. The air permeability layer 12 may include at least one of clay particles, diatomaceous earth, plant-based filler, non-layered silicate, unexpanded graphite, and porous and / or fine particles thereof. In the air permeability layer 12, at least one of the clay particles, diatomaceous earth, plant-based filler, non-layered silicate, unexpanded graphite, and porous and / or fine particles thereof may form gaps in the porous medium that generate an acoustic absorption profile. The configuration of this acoustic absorption profile can be adjusted by a combination of particle properties.

[0061] As another example, the airflow resistance layer 12 may include at least one of a fibrous nonwoven fabric layer and an adhesive fiber. These fibers may be made of polypropylene, polyethylene terephthalate, styrene-isoprene-styrene, or a polyethylene / polypropylene copolymer. When the above profile of the airflow resistance layer 12 is formed of fine particles, the composition of the particles, the surface area of ​​the particles, and the size of the particles are not particularly limited. An exemplary airflow resistance layer 12 may include a filler, and the particle size of the filler is 1 μm or more and 100 μm or less. The specific surface area of ​​the airflow resistance layer 12 is 0.1 m 2 / g or more and 800m 2 / g or less.

[0062] The airflow resistance value of the airflow resistance layer 12 may be 100 MKS Rayls or more and 8000 MKS Rayls or less. The airflow resistance value of the airflow resistance layer 12 may be 100 MKS Rayls or more and 8000 MKS Rayls or less, 20 MKS Rayls or more and 3000 MKS Rayls or less, or 50 MKS Rayls or more and 1000 MKS Rayls or less. The airflow resistance value of the airflow resistance layer 12 is 20MKS Rayls, 30MKS Rayls, 40MKS Rayls, 50MKS Rayls, 70MKS Rayls, 100MKS Rayls, 200MKS Rayls, 300MKS Rayls, 400MKS Rayls, 500MKS Rayls, 600MKS Rayls, 700MKS Rayls, 1000MKS Rayls, 1100MKS Rayls, 1200MKS Rayls, 1500MKS Rayls, 1700MKS Rayls, 2000MKS Rayls, 3000MKS Rayls, 3500MKS Rayls, 4000MKS Rayls, 5000MKS Rayls, 5500MKS Rayls, 6000MKS Rayls, 6500MKS Rayls, 7000MKS Rayls, 7500MKS Rayls It may be either Rayls or 8000MKS Rayls.

[0063] The filler of airflow resistive layer 12 may be non-uniformly dispersed in the porous layer of airflow resistive layer 12. Airflow resistive layer 12 may include a nonwoven fibrous web. The filler may be diatomaceous earth, a vegetable-based filler, unexpanded graphite, a polyolefin foam, or a combination thereof. Furthermore, the filler of the ventilation resistance layer 12 is 1 mass% or more and 99 mass% or less, 10 mass% or more and 90 mass% or less, 15 mass% or more and 85 mass% or less, 20 mass% or more and 80 mass% or less, 1 mass% or less, 1 mass% or more, 2 mass%, 3 mass%, 4 mass%, 5 mass%, 7 mass%, 10 mass%, 1 It may be 2% by mass, 15% by mass, 20% by mass, 30% by mass, 35% by mass, 40% by mass, 45% by mass, 50% by mass, 55% by mass, 60% by mass, 65% by mass, 70% by mass, 75% by mass, 80% by mass, 85% by mass, 90% by mass, 95% by mass, 97% by mass, 98% by mass, or 99% by mass. The filler of the airflow resistive layer 12 may be at least one of fine fillers such as clay, diatomaceous earth, graphite, glass foam, porous fillers, polymeric fillers, non-layered silicates, plant-based fillers, and combinations thereof.

[0064] As described above, the air permeability layer 12 may have a porous layer, and the average inter-fiber distance of the porous layer may be greater than 0 μm and less than or equal to 100 μm. The average inter-fiber distance of the air permeability layer 12 may be 1 μm or more and 1000 μm or less, 10 μm or more and 500 μm or less, or 20 μm or more and 300 μm or less. Furthermore, the average inter-fiber distance of the air permeability layer 12 may be any of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 7 μm, 10 μm, 11 μm, 12 μm, 15 μm, 17 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 150 μm, 170 μm, 200 μm, 250 μm, 300 μm, 400 μm, 450 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, and 1000 μm.

[0065] As described above, the air permeability layer 12 may be composed of fine particles. In this case, the average particle spacing of the air permeability layer 12 may be 20 μm or more and 4000 μm or less, 50 μm or more and 2000 μm or less, or 100 μm or more and 1000 μm or less. The average particle spacing of the air permeability layer 12 may be less than 20 μm, 20 μm or less, or more than 4000 μm. In addition, the average particle spacing of the air permeability layer 12 may be any of 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 150 μm, 170 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 1100 μm, 1200 μm, 1500 μm, 1700 μm, 2000 μm, 2500 μm, 3000 μm, 3500 μm, and 4000 μm.

[0066] Although the thickness T of the air permeability layer 12 is exemplified above, it is not particularly limited to the exemplified values. Furthermore, the exemplary thickness T of the air permeability layer 12 may be 1 μm or more and 10 cm or less, 30 μm or more and 1 cm or less, or 50 μm or more and 500 μm or less. The thickness T of the air permeability layer 12 may be any of 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 100 μm, 200 μm, 500 μm, 1 mm, 2 mm, 5 mm, 10 mm, 20 mm, 50 mm, 70 mm, and 100 mm.

[0067] When the air permeability resistance layer 12 contains the above-mentioned filler, it is possible to improve the sound absorption performance for various frequency bands. The sound frequency band in which the air permeability resistance layer 12 exhibits high sound absorption performance may be, for example, 50 Hz or more and 500 Hz or less, or 500 Hz or more. The sound frequencies that the air permeability resistance layer 12 targets are 50 Hz, 55 Hz, 60 Hz, 65 Hz, 70 Hz, 75 Hz, 80 Hz, 85 Hz, 90 Hz, 95 Hz, 100 Hz, 105 Hz, 110 Hz, 115 Hz, 120 Hz, 125 Hz, 130 Hz, 135 Hz, 140 Hz, 145 Hz, 150 Hz, 155 Hz, 160 Hz, 165 Hz, 170 Hz, 175 Hz, and 180 Hz. Hz, 180Hz, 185Hz, 190Hz, 195Hz, 200Hz, 230Hz, 240Hz, 250Hz, 260Hz, 270Hz, 280Hz, 290Hz, 300Hz, 400Hz, 500Hz, 700Hz, 1000Hz, 2000Hz, 3000Hz, 4000Hz, 5000Hz, 7000Hz, and 10000Hz.

[0068] The airflow resistant layer 12 may include a nonwoven fabric layer or may include glass fibers. The glass fibers are typically made by melting silica or other minerals in a furnace. The molten silica or the like may be forced through a spinneret containing small orifices to produce a molten stream, which is then cooled by being guided by a stream of hot air. The characteristics of the airflow resistant layer 12 have been described above, but the core layer 11 may also have the above-mentioned characteristics.

[0069] Next, a method for producing a sound-absorbing material according to an embodiment will be described with reference to Figs. 3 to 8. The method for producing a sound-absorbing material according to the present disclosure is not limited to the examples described below. First, as shown in Figs. 3 and 4, a material 22 for forming the airflow resistance layer 12 is prepared (a step of preparing a material for forming the airflow resistance layer). As a specific example, a laminate in which the material 22 for the airflow resistance layer 12 and the material 23 for the first cover layer 13 are integrated is prepared, and the laminate is sandwiched between a mold M1 (first mold) and a mold M2. When the first cover layer 13 is not provided, only the material 22 may be sandwiched between the mold M1 and the mold M2.

[0070] As described above, the material 22 constituting the airflow resistance layer 12 is sandwiched between the mold M1 to form the airflow resistance layer 12 (step of forming the airflow resistance layer). For example, the first cover layer 13 may be molded together with the airflow resistance layer 12. Furthermore, the material 22 and the material 23 sandwiched in the direction in which the mold M1 and the mold M2 face each other (the up-down direction in FIG. 4 ) on the outer side of the sound-absorbing material 1 than the portion where the rising portion 4 is formed (the portion extending in the third direction D3) may be molded as the thin plate layer 15.

[0071] When the air permeability layer 12 is being molded as described above, the thickness of the air permeability layer 12 may be adjusted to be constant using a calendar roll. Alternatively, the thickness of the air permeability layer 12 may be adjusted to be constant by pressing. Alternatively, molding may be performed so that the thickness of the air permeability layer 12 sandwiched between the molds M1 and M2 is constant by making the width of the gap formed between the molds M1 and M2 constant. Note that after the thickness of the air permeability layer 12 is made constant using a calendar roll, it may be pressed to a final reference thickness T.

[0072] After the molding of the air permeability layer 12 is completed, as shown in FIG. 5 and FIG. 6, the mold M2 is removed from the air permeability layer 12 and the mold M1, and the material 21 for the core layer 11 is prepared (a step of preparing a material for the core layer). Then, the material 21 is sandwiched between the air permeability layer 12 and the mold M3 (a second mold). The mold M3 is a mold different from the mold M2, and is, for example, flat. The material for the second cover layer 14 together with the material 21 for the core layer 11 may be sandwiched between the material 21 for the core layer 11 and the mold M3. Alternatively, the molded air permeability layer 12 may be left in the mold M1, the mold M2 may be changed to the mold M3, and the material 21 for the core layer 11 may be prepared and sandwiched between the air permeability layer 12 and the mold M3. In this case, the core layer 11 can be molded without removing the molded air permeability layer 12.

[0073] 7 and 8, the material 21 is sandwiched between the air permeability layer 12 and a mold M3 to form the core layer 11 (core layer forming step). The second cover layer 14 may be formed together with the core layer 11. After the core layer 11 is formed in this manner, the mold M3 is removed to complete the sound-absorbing material 1. As described above, in the embodiment, the air permeability layer 12 and the core layer 11 are formed separately in two stages, so that the thickness T of the air permeability layer 12 can be adjusted easily and with high precision.

[0074] Next, the effects of the sound-absorbing material and the manufacturing method of the sound-absorbing material according to the embodiment will be described. As illustrated in Fig. 2, the sound-absorbing material 1 has a rising portion 4 rising from an attachment portion P, and a facing portion 5 facing a component on the opposite side of the rising portion 4 from the attachment portion P. Therefore, the shape of the sound-absorbing material 1 is three-dimensional, and therefore it can be used for components having complex shapes.

[0075] Each of the rising portion 4 and the facing portion 5 includes a core layer 11 and an airflow resistance layer 12. Therefore, the core layer 11 absorbs sound while the airflow resistance layer 12 moderately suppresses airflow, thereby improving sound absorption performance. In addition, the variation in thickness T of the airflow resistance layer 12 is 40% or less of the average value of the thickness T in at least a portion of the sound absorption material 1. In this case, the variation in thickness T of at least a portion of the airflow resistance layer 12 is constant, so that the sound absorption coefficient of the sound absorbing material 1 can be increased. Therefore, the sound absorption performance can be improved.

[0076] In the exemplary sound-absorbing material 1, the variation in thickness T of the airflow resistance layer 12 may be 40% or less of the average value in 80% or more of the region of the sound-absorbing material 1 that includes the facing portion 5 and the rising portion 4 but does not include the edge portion 2. In this case, since the variation in thickness T is 40% or less in 80% or more of the region of the sound-absorbing material 1, the thickness T of the airflow resistance layer 12 can be made even more constant, which contributes to a further improvement in the sound absorption coefficient.

[0077] In the exemplary sound-absorbing material 1, the thickness T of the air permeability layer 12 may be 1 mm or more and 6 mm or less. In this case, by having the thickness T of the air permeability layer 12 be 1 mm or more and 6 mm or less, the thickness T of the air permeability layer 12 can be made appropriate and uniform, thereby further improving the sound absorption efficiency.

[0078] In the exemplary sound-absorbing material 1, the airflow resistance value of the airflow resistance layer 12 may be within a range of a reference value ±120 Rayls. In this case, since the airflow resistance value is within a range of a reference value ±120 Rayls, the airflow resistance value can be kept constant at an appropriate value based on the reference value, and sound absorbing performance can be improved.

[0079] In the exemplary sound-absorbing material 1, the airflow resistance value of the airflow resistance layer 12 may be 300 Rayls or more and 1100 Rayls or less. In this case, since the airflow resistance value is 300 Rayls or more and 1100 Rayls or less, the airflow resistance value can be kept constant at an appropriate value, which contributes to further improvement of the sound absorption performance.

[0080] In the exemplary sound-absorbing material 1, the air permeability resistance layer 12 may be located on the component side as viewed from the core layer 11. In this case, since the air permeability resistance layer 12 is provided on the component side, the air permeability resistance layer 12 can absorb sound more effectively. Therefore, high sound absorption performance can be maintained.

[0081] In the exemplary sound-absorbing material 1, at least one of the airflow resistance layer 12 and the core layer 11 may contain microfibers. In this case, it is possible to achieve a reduction in weight while maintaining high sound-absorbing performance.

[0082] In the method of manufacturing a sound-absorbing material according to the embodiment, first, the material 22 of the air permeability layer 12 is sandwiched between molds M1 and M2 to form the air permeability layer 12. Therefore, by first forming the air permeability layer 12 by sandwiching it between molds M1 and M2, the thickness T of the air permeability layer 12 can be made constant by molds M1 and M2. Then, the core layer 11 is formed using molds M1 and M3 for the air permeability layer 12 whose thickness T has been made constant. Therefore, a sound-absorbing material 1 having high sound-absorbing performance and including the air permeability layer 12 and core layer 11 with constant thicknesses can be manufactured.

[0083] As described above, the step of forming the air permeability layer 12 may include a step of adjusting the thickness T of the air permeability layer 12 by pressing, or by using a calendar roll and pressing. In this case, the thickness T of the air permeability layer 12 is adjusted by at least one of the calendar roll and pressing, so that the thickness T of the air permeability layer 12 can be made constant. As described above, the thickness of the air permeability layer 12 may be made constant by using the calendar roll, and then the final thickness T may be achieved by pressing.

[0084] The above describes the embodiments of the sound-absorbing material and the manufacturing method of the sound-absorbing material according to the present disclosure. However, the present disclosure is not limited to the above-mentioned embodiments. The present disclosure can be modified in various ways without changing the gist of the claims. In other words, the shape, size, material, number, and arrangement of each part of the sound-absorbing material, as well as the content and order of the steps of the manufacturing method of the sound-absorbing material, can be modified as appropriate without changing the gist of the above.

[0085] Next, various examples of the sound-absorbing material will be described with reference to Figs. 9 to 11. Note that the present disclosure is not limited to the examples described below. First, the sound-absorbing materials according to Examples 1 to 6 will be described. The specifications of each of the sound-absorbing materials according to Examples 1 to 6 are shown below.

[0086] (Example 1) The sound-absorbing material of Example 1 includes a core layer 11 , a first cover layer 13 and a second cover layer 14 , and does not include an air flow resistance layer 12 . The melt-blown fibers of the core layer 11 are made of PP resin in a melt-blown process to produce melt-blown fibers with a fiber diameter of 5 μm and a weight per unit area of ​​315 g / m 2 The staple fibers for the core layer 11 were PET short fibers (6.6 dT x 38 mm) of 71 g / m 2 The binder fiber of the core layer 11 is a fiber (4.4dT×38mm) 34g / m made of PET with a melting point of 260°C as the core part and PET with a low melting point of 110°C as the sheath part. 2 The fiber was blown onto the melt-blown fiber so that it would join the fiber flow immediately after it was blown out, and the total weight per unit area was 420 g / m 2 A mixed web of 40 g / m2 black PP spunbond was used as a cover material for this mixed web. 2 The two are then pasted together using a spray-type hot melt adhesive, and the other side is covered with white SMS 13g / m 2 The layers were attached by spraying hot melt to produce a single-layer sound absorbing material for the core layer 11. The raw sheet was placed in a heat press and heated to 130° C. for 30 seconds to produce a core layer 11 with a thickness of 10 mm. The weight per unit area was determined by cutting the original core layer 11 into five samples of 10 cm×10 cm, measuring the weight of each sample, and calculating the weight per unit area from the average weight. The thickness of the core layer was measured using a measurement method based on ASTM F778-88. That is, five samples were prepared by cutting the original roll into 10 cm x 10 cm pieces. The samples were placed in the center of the two upper and lower plates. The distance between the upper and lower plates was then adjusted to a height of 5 cm ± 0.2 cm, the upper plate was removed from this height, and allowed to fall onto the lower plate under its own weight. In this state, the plate was left for 3 seconds, and the distance between the upper and lower plates was measured with the built-in micrometer. (Example 2) The same raw material of the core layer 11 as in Example 1 was finished by hot pressing under the same conditions as in Example 1 so that the thickness of the core layer 11 was 20 mm. The method of measuring the weight per unit area and the method of measuring the thickness were the same as in Example 1. (Example 3) The same raw material of the core layer 11 as in Example 1 was finished by hot pressing under the same conditions as in Example 1 so that the thickness of the core layer 11 was 30 mm. The method of measuring the weight per unit area and the method of measuring the thickness were the same as in Example 1.

[0087] (Example 4) The sound-absorbing material of Example 4 includes a core layer 11, an airflow resistance layer 12, a first cover layer 13 and a second cover layer 14, similar to the sound-absorbing material 1 of FIG. The core layer 11 is made of meltblown fibers 240 g / m 2 , PET staple fiber 54g / m 2 , binder fiber 26g / m 2 , total 320g / m 2 Then, one side was covered with white SMS 13g / m 2 The resulting raw material was attached by spraying hot melt to produce a raw material for the core layer 11. This raw material was sandwiched in a hot press, and the thickness of the core layer 11 was adjusted to 9.3 mm at a temperature of 130° C. for a holding time of 30 seconds. The airflow resistance layer 12 was made of meltblown fiber 50 g / m 2 , PET staple fiber 34g / m 2 , binder fiber 16g / m 2 , total 100g / m 2 Then, one side was covered with black spunbond 40 / m 2 The resulting sheet was attached using a spray-type hot melt to produce a base sheet of the airflow resistance layer 12. This base sheet was placed in a heat press and held at 130° C. for 30 seconds until the thickness of the airflow resistance layer 12 was 0.7 mm. These core layer 11 and air resistance layer 12 were laminated to obtain Example 4. The method of measuring the weight per unit area and the method of measuring the thickness were the same as in Example 1. (Example 5) An original sheet of the core layer 11 identical to that in Example 4 was finished by heat pressing under the same conditions as in Example 4 so that the thickness of the core layer 11 was 19.3 mm. The same air permeability layer 12 as in Example 4 was used, and the core layer 11 and the air permeability layer 12 were laminated to obtain Example 5. The method of measuring the weight per unit area and the method of measuring the thickness were the same as in Example 1. (Example 6) An original sheet of the core layer 11 identical to that in Example 4 was finished by heat pressing under the same conditions as in Example 4 so that the thickness of the core layer 11 was 29.3 mm. The same air permeability layer 12 as in Example 4 was used, and the core layer 11 and the air permeability layer 12 were laminated to obtain Example 6. The methods for measuring the weight per unit area and the thickness were the same as in Example 1.

[0088] The graph in FIG. 9 shows an example of the experimental results confirming the sound absorption performance for the above Examples 1 to 6. The sound absorption performance was measured by the two-microphone method based on ASTM E 1050-98 ("Impedance and Absorption Using A Tube, Two Microphones and A Digital Frequency Analysis System."). The frequency measurement range was 500 Hz to 4000 Hz. The two-microphone method is a method in which the incident and reflected components of the sound pressure inside a tube are measured with two microphones to determine the sound absorption coefficient. In addition to the sound absorption performance, the airflow resistance was also measured. The airflow resistance was measured based on the method previously specified in ASTM C 522. The sample was cut into a circle with a diameter of 5.25 inches (133.3 mm) and fixed to a sample stage. The sheet surface of this sample was measured at 100 cm2. 2 Compressed air was supplied perpendicularly to the surface of the air permeability layer 12, and the differential pressure generated in the perpendicular direction to the surface of the air permeability layer 12 was measured to calculate the air permeability resistance.

[0089] The horizontal axis of the graph in Fig. 9 represents the frequency of the sound applied to the sound-absorbing material, and the vertical axis of the graph in Fig. 9 represents the sound absorption coefficient of the sound applied to the sound-absorbing material. As shown in Fig. 9, the sound-absorbing materials of Examples 4 to 6, which have an air resistance layer 12 with a thickness of 0.7 mm, had an air resistance value of 1596 Rayls, and achieved a high sound absorption coefficient in the low-frequency range of 1000 Hz or less and a low sound absorption coefficient in the high-frequency range.

[0090] Next, Examples 7 to 9 will be described below with reference to FIG. (Example 7) The sound absorbing material of Example 7 differs from Example 4 in the thickness of the core layer 11 and the thickness of the airflow resistance layer 12. In Example 7, the thickness of the core layer 11 was 7 mm, and the thickness of the airflow resistance layer 12 was 3 mm. Specifically, the core layer 11 was made from the same raw material as in Example 4 and finished to a thickness of 7 mm by heat pressing under the same conditions as in Example 4. The air permeability layer 12 was made from the same raw material as in Example 4 and finished to a thickness of 3 mm by heat pressing under the same conditions as in Example 4. These core layers 11 and air permeability layer 12 were then stacked to produce Example 7. The methods for measuring the weight per unit area and the thickness were the same as in Example 1. (Example 8) In Example 8, the core layer 11 was made from the same raw material as in Example 4, and finished to a thickness of 17 mm by heat pressing under the same conditions as in Example 4. The air permeability resistance layer 12 was the same as in Example 7. These core layers 11 and air permeability resistance layers 12 were stacked to obtain Example 8. The methods for measuring the weight per unit area and the thickness were the same as in Example 1. (Example 9) In Example 9, the core layer 11 was made from the same raw material as in Example 4, and finished to a thickness of 27 mm by heat pressing under the same conditions as in Example 4. The air permeability resistance layer 12 was the same as in Example 7. These core layers 11 and air permeability resistance layers 12 were stacked to obtain Example 9. The methods for measuring the weight per unit area and the thickness were the same as in Example 1.

[0091] Fig. 10 is a graph showing the results of confirming the sound absorption performance of Examples 7 to 9 and the previously described Examples 1 to 3. For Examples 7 to 9, the airflow resistance was measured as well as the sound absorption performance. The method for measuring the airflow resistance was the same as that used for Examples 4 to 6. As shown in Fig. 10, the sound absorbing materials of Examples 7 to 9, which have an airflow resistance layer 12 with a thickness of 3 mm, had an airflow resistance of 428 Rayls, demonstrating that a high sound absorption coefficient was obtained over a wide frequency band.

[0092] Next, Examples 10 to 12 will be described below. (Example 10) The sound absorbing material of Example 10 differs from Example 4 in the thickness of the core layer 11 and the thickness of the airflow resistance layer 12. In Example 10, the thickness of the core layer 11 was 4 mm, and the thickness of the airflow resistance layer 12 was 6.2 mm. Specifically, the core layer 11 was made from the same raw material as in Example 4 and finished to a thickness of 4 mm by heat pressing under the same conditions as in Example 4. The air permeability layer 12 was made from the same raw material as in Example 4 and finished to a thickness of 6.2 mm by heat pressing under the same conditions as in Example 4. These core layers 11 and air permeability layer 12 were then stacked to obtain Example 10. The methods for measuring the weight per unit area and the thickness were the same as in Example 1. (Example 11) In Example 11, the core layer 11 was made from the same raw material as in Example 4, and finished to a thickness of 14 mm by heat pressing under the same conditions as in Example 4. The air permeability resistance layer 12 was the same as in Example 10. These core layers 11 and air permeability resistance layers 12 were stacked to obtain Example 11. The methods for measuring the weight per unit area and the thickness were the same as in Example 1. (Example 12) In Example 12, the core layer 11 was made from the same raw material as in Example 4, and finished to a thickness of 24 mm by heat pressing under the same conditions as in Example 4. The air permeability resistance layer 12 used was the same as in Example 10. These core layers 11 and air permeability resistance layers 12 were stacked to obtain Example 12. The methods for measuring the weight per unit area and the thickness were the same as in Example 1.

[0093] Fig. 11 is a graph showing the results of confirming the sound absorption performance of the above-mentioned Examples 10 to 12 and Examples 1 to 3. For Examples 10 to 12, the airflow resistance value was measured as well as the sound absorption performance. The method of measuring the airflow resistance value was the same as that used for Examples 4 to 6. As shown in Fig. 11, the sound absorbing materials of Examples 10 to 12 having an airflow resistance layer 12 with a thickness of 6.2 mm had an airflow resistance value of 271 Rayls, and although a high sound absorption coefficient was obtained in the high frequency range of the frequency band of 2000 Hz or more, the sound absorption coefficient was low in the low frequency range.

[0094] 9 to 11, the thickness of the air resistance layer 12 was set to 3 mm and the air resistance value was set to 428 Rayls as the reference values, and the results of verification in which the thickness of the air resistance layer 12 was changed by ±1 mm from the reference values ​​are shown in Fig. 12. Fig. 12 shows the results of an experiment in which a comparative example (Example 3, no air resistance layer) did not have an air resistance layer 12, Example 9 (thickness 3 mm) had an air resistance layer 12 with a thickness of 3 mm, and Example 9 in which the thickness of the air resistance layer 12 was further changed to 2 mm or 4 mm.

[0095] In an example in which the air permeability layer 12 is 2 mm thick, the core layer 11 was finished to a thickness of 28 mm using the same raw material as in Example 4 by heat pressing under the same conditions as in Example 4. The air permeability layer 12 was finished to a thickness of 2 mm using the same raw material as in Example 4 by heat pressing under the same conditions as in Example 4. These core layers 11 and air permeability layers 12 were stacked to obtain a 2 mm sample. As mentioned above, the example in which the air permeability layer 12 is 3 mm thick is the same as Example 9.

[0096] In the example where the thickness of the airflow resistance layer 12 is 4 mm, the core layer 11 was finished to a thickness of 26 mm under the same conditions as in Example 4 by heat pressing on the same original roll as in Example 4. The airflow resistance layer 12 was finished to a thickness of 4 mm under the same conditions as in Example 4 by heat pressing on the same original roll as in Example 4. These core layers 11 and airflow resistance layers 12 were stacked to obtain 4 mm samples. For each of these examples shown in FIG. 12, the airflow resistance value was measured together with the sound absorption performance. The method for measuring the airflow resistance value was the same as that used for Examples 4 to 6.

[0097] 12, it can be seen that not only the example (Example 9) with a thickness of 3 mm, but also the sound absorbing material with an airflow resistance layer 12 with a thickness of 2 mm or 4 mm can obtain a higher sound absorption coefficient than the example (Example 3) without the airflow resistance layer 12. The airflow resistance value was 534 Rayls when the thickness of the airflow resistance layer 12 was 2 mm, and the airflow resistance value was 317 Rayls when the thickness of the airflow resistance layer 12 was 4 mm. It was therefore found that good results could be obtained when the variation in thickness of the airflow resistance layer 12 was within the reference value (3 mm) ±40% and the airflow resistance value was within the reference value (428 Rayls) ±120 Rayls.

[0098] Example 1 and Comparative Example 1 will be described below with reference to FIG. Example 1 In Example 1, the sound-absorbing material was produced by separately molding the airflow resistance layer 12 and the core layer 11 in two stages as illustrated in Figures 3 to 8. Example 1 included the core layer 11, the airflow resistance layer 12, the first cover layer 13 and the second cover layer 14 described below. The air permeability layer 12 was made using the same raw material as in Example 4, and this air permeability layer 12 was placed in a metal mold and molded into a 3D shape with a thickness of 3 mm at a temperature of 130° C. for a holding time of 30 seconds. One piece of the molded air permeability layer 12 was also taken out at this stage, and the thickness of the air permeability layer 12 was measured in a non-contact manner. The core layer 11 was made from the same raw material as in Example 4, and was placed in a metal mold together with the molded airflow resistance layer 12 as described above, and molded at a temperature of 130° C. for a holding time of 30 seconds. The completed sound absorbing material was then placed in a reverberation chamber to measure the sound absorption coefficient. After the measurement, the sample of the sound absorbing material was cut and the cross section was visually observed as shown in FIG. 15(b) to confirm that the air flow resistance layer 12 was molded to a constant thickness. The thickness of the 3D molded air flow resistance layer 12 was measured using a non-contact laser displacement meter. The thickness of the opposing portion 5 and the rising portion 4 in the air flow resistance layer 12 of Example 1 are shown in Table 1 below. [Table 1]

[0099] Comparative Example 1 The sound absorbing material according to Comparative Example 1 includes a core layer 11 , a first cover layer 13 and a second cover layer 14 , and does not include an air flow resistance layer 12 . For Comparative Example 1 not having the air permeability layer 12, the same original fabric as in Example 1 was used, placed in the metal mold described above, and molded into a 3D shape having a single layer of core layer 11 at a temperature of 130° C. for a holding time of 30 seconds, following only the steps shown in Figures 6 to 8. The cross section of the sample after measurement was cut and observed as shown in Figure 15(a).

[0100] The sound absorption coefficient was measured for Example 1 and Comparative Example 1. The sound absorption coefficient of each molded sound absorbing material was measured in accordance with JIS A 1409 using a reverberation room sound absorption coefficient and sound transmission loss measurement system ABLoss manufactured by Nihon Acoustic Engineering Co., Ltd. As a result, as shown in Fig. 13, it was found that the sound absorbing material of Example 1, in which the air permeability resistance layer 12 and the core layer 11, both 3 mm thick, were molded in two stages, had a high sound absorption coefficient in a wide frequency range of 3000 Hz or less (especially in the low frequency range).

[0101] Next, Example 2 and Comparative Example 2 will be described below with reference to FIG. Example 2 The same raw material as in Example 4 was used for the air permeability layer 12, which was placed in the metal mold described above and molded into a 3D shape with a thickness of 3 mm at a temperature of 130° C. for a holding time of 30 seconds. At this point, one of the molded air permeability layers 12 was taken out and its thickness was measured without contact. The core layer 11 was formed in the same manner as in Example 1, using PP resin as the melt-blown fiber, and melt-blown fiber with a fiber diameter of 5 μm was used at 628 g / m per unit area by the melt-blown process. 2 The porous particles were spun to obtain a density of 157 g / m of activated carbon. 2 The fiber was blown onto the melt-blown fiber so that it would join the fiber flow immediately after it was blown out, resulting in a total weight per unit area of ​​785 g / m 2 A mixed web of white SMS 17g / m was produced on the side opposite to the sound source of the airflow resistance layer 12. 2was attached by spraying hot melt to form the core layer 11. This core layer 11 was placed in a metal mold together with the molded airflow resistance layer 12 as described above, and molded at a temperature of 130° C. for a holding time of 30 seconds. The completed sound absorbing material was then placed in a reverberation chamber to measure the sound absorption coefficient. After the measurement, the sample was cut and the cross section was observed as shown in FIG. 16(b) to confirm that the air flow resistance layer 12 was molded to a constant thickness. The thickness of the 3D molded air flow resistance layer 12 was measured using a non-contact laser displacement meter. The thickness of the opposing portion 5 and the rising portion 4 in the air flow resistance layer 12 of Example 2 are shown in Table 2 below. [Table 2] Comparative Example 2 In Comparative Example 2, the same air permeability resistance layer 12 as in Example 2 was used. The same core layer 11 as in Example 2 was also used. The core layer 11 and the air permeability resistance layer 12 were simultaneously placed in a metal mold and molded into a 3D shape at a temperature of 130°C and a holding time of 30 seconds. The completed sound absorbing material was placed in a reverberation chamber and the sound absorption coefficient was measured. In addition, the sample after the measurement was cut and the cross section was observed as shown in FIG. 16(a) and compared with Example 2. Note that, as shown in FIG. 16(a), in Comparative Example 2, the boundary between the core layer 11 and the air permeability resistance layer 12 was unclear, so the air permeability resistance layer 12 is not shown.

[0102] The sound absorption coefficient was measured for Example 2 and Comparative Example 2. The sound absorption coefficient of each molded sound absorbing material was measured in accordance with JIS A 1409 using a reverberation room sound absorption coefficient and sound transmission loss measurement system, ABLoss, manufactured by Nihon Acoustic Engineering Co., Ltd. As a result, as shown in Fig. 14, it was found that Example 2, which includes an air resistance layer 12 whose thickness is adjusted to 3 mm, can obtain a high sound absorption coefficient in a wide frequency range of 3000 Hz or less (especially in the low frequency range) compared to Comparative Example 2, whose thickness is not adjusted. [Explanation of symbols]

[0103] 1...sound-absorbing material, 2...edge, 2b...first edge, 2c...second edge, 2d...inclined edge, 2f...hole, 3...protrusion, 3b...first protrusion, 3c...second protrusion, 3d...recess, 4...raised portion, 5...opposing portion, 11...core layer, 12...airflow resistance layer, 13...first cover layer, 14...second cover layer, 15...thin plate layer, 21...material constituting core layer, 22...material constituting airflow resistance layer, 23...material, C...corner, D1...first direction, D2...second direction, D3...third direction, M1...type (first type), M2...type, M3...type (second type), P...mounting portion.

Claims

1. A sound-absorbing material that absorbs sound from a part, a rising portion rising from a mounting portion to which the sound absorbing material is attached, and a facing portion facing the component on an opposite side of the rising portion from the mounting portion, Each of the rising portion and the facing portion includes a core layer and a ventilation resistance layer, In at least a part of the facing portion and the rising portion, the variation in thickness of the air permeability resistance layer is 40% or less of the average thickness of the air permeability resistance layer. Sound absorbing material.

2. In an area of ​​the sound absorbing material including the facing portion and the rising portion but not including the edge portion, the variation in thickness of the air flow resistance layer is 40% or less of the average value. The sound-absorbing material according to claim 1.

3. The thickness of the air flow resistance layer is 1 mm or more and 6 mm or less. The sound-absorbing material according to claim 1 or 2.

4. The airflow resistance value of the airflow resistance layer is within a range of a reference value ±120 Rayls. The sound-absorbing material according to any one of claims 1 to 3.

5. The air flow resistance value of the air flow resistance layer is 300 Rayls or more and 1100 Rayls or less. The sound-absorbing material according to any one of claims 1 to 4.

6. The airflow resistance layer is located on the component side as viewed from the core layer. The sound-absorbing material according to any one of claims 1 to 5.

7. At least one of the air flow resistance layer and the core layer contains microfibers. The sound-absorbing material according to any one of claims 1 to 6.

8. A method for producing a sound-absorbing material having a core layer and an air flow resistance layer, comprising the steps of: preparing a material constituting the air permeability layer; a step of sandwiching a material constituting the air permeability layer between a first mold to form the air permeability layer; a step of sandwiching a material constituting the core layer between the air permeability layer and a second mold to form the core layer; A method for manufacturing a sound-absorbing material comprising:

9. The step of forming the air permeability layer includes a step of adjusting the thickness of the air permeability layer by a press or a calender roll and a press. A method for producing the sound absorbing material according to claim 8.

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