Composite sound-absorbing material and method for manufacturing composite sound-absorbing material

Abstract

This invention provides a composite sound-absorbing material that can achieve a high sound-absorbing effect even with reduced thickness compared to conventional sound-absorbing materials. It also provides a method for manufacturing such a composite sound-absorbing material. [Solution] A composite sound-absorbing material 1 comprises a foam layer 10 having a resin foam 12 and a nanofiber layer 20 laminated on the foam layer 10 and having nonwoven nanofibers 22. The composite sound-absorbing material 1 can be manufactured by a manufacturing method that includes, for example, a foam layer preparation step of preparing the foam layer 10 and a nanofiber layer formation step of forming a nanofiber layer 20 having nonwoven nanofibers 22 using the foam layer 10 as a base material and an electrospinning method.

Description

[Technical Field]

[0001] This invention relates to a composite sound-absorbing material and a method for manufacturing a composite sound-absorbing material. [Background technology]

[0002] Conventionally, sound-absorbing materials using resin foam are known (see, for example, Patent Document 1). These sound-absorbing materials are used, for example, as interior materials for building materials, automobiles, aircraft, etc. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-77134 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Incidentally, the sound-absorbing effect of sound-absorbing materials made of resin foam basically depends on the thickness of the resin foam. Therefore, conventional sound-absorbing materials have the problem that they cannot achieve a high sound-absorbing effect while reducing the thickness.

[0005] The present invention was made to solve the above problems, and aims to provide a composite sound-absorbing material that can achieve a high sound-absorbing effect even with reduced thickness compared to conventional sound-absorbing materials. It also aims to provide a method for manufacturing such a composite sound-absorbing material. [Means for solving the problem]

[0006] [1] A composite sound-absorbing material according to one embodiment of the present invention is characterized by comprising a foam layer having a resin foam and a nanofiber layer laminated on the foam layer and having nonwoven nanofibers.

[0007] [2] In the composite sound-absorbing material according to one embodiment of the present invention, the resin foam is preferably a melamine foam.

[0008] [3] In the composite sound-absorbing material according to one embodiment of the present invention, the non-woven nanofibers are preferably made of a thermoplastic polyurethane-based material.

[0009] [4] In the composite sound-absorbing material according to one embodiment of the present invention, it is preferable to further include an adhesive for joining the resin foam and the non-woven nanofibers.

[0010] [5] In the composite sound-absorbing material according to one embodiment of the present invention, the adhesive is preferably a low-melting-point nanofiber made of a low-melting-point resin having a melting point lower than the melting points of the resin foam and the non-woven nanofibers.

[0011] [6] In the composite sound-absorbing material according to one embodiment of the present invention, it is preferable that the adhesive partially joins the foam layer and the nanofiber layer.

[0012] [7] In the composite sound-absorbing material according to one embodiment of the present invention, the resin foam preferably has a thickness within the range of 1 mm to 40 mm.

[0013] [8] In the composite sound-absorbing material according to one embodiment of the present invention, the non-woven nanofibers preferably have a laminated amount within the range of 2 g / m 2 ~7 g / m 2 of the range.

[0014] [9] In the composite sound-absorbing material according to one embodiment of the present invention, the resin foam preferably has a density within the range of 1 kg / m 3 ~20 kg / m 3 of the range.

[0015]

[10] In the composite sound-absorbing material according to one embodiment of the present invention, the non-woven nanofibers preferably have an average pore diameter within the range of 0.8 μm to 1.3 μm.

[0016]

[11] The manufacturing method of the composite sound-absorbing material according to one embodiment of the present invention includes a foam layer preparation step of preparing a foam layer having a resin foam, and a nanofiber layer formation step of forming a nanofiber layer having a non-woven nanofiber using an electrospinning method with the foam layer as a base material.

[0017]

[12] In the manufacturing method of the composite sound-absorbing material according to one embodiment of the present invention, it is preferable to further include a joining step of joining the resin foam and the non-woven nanofiber after the nanofiber layer formation step.

[0018]

[13] The manufacturing method of the composite sound-absorbing material according to one embodiment of the present invention includes a foam layer preparation step of preparing a foam layer having a resin foam, and a nanofiber layer pasting step of pasting a nanofiber layer having a non-woven nanofiber to the foam layer using an adhesive.

Effect of the Invention

[0019] The composite sound-absorbing material of the present invention includes a foam layer having a resin foam and a nanofiber layer laminated on the foam layer and having a non-woven nanofiber. Therefore, as shown in the examples described later, it becomes a composite sound-absorbing material that can obtain a high sound-absorbing effect even when the thickness is reduced as compared with conventional sound-absorbing materials.

[0020] The manufacturing method of the composite sound-absorbing material of the present invention includes a foam layer preparation step and a nanofiber layer formation step or a nanofiber layer pasting step, so that it is a manufacturing method of a composite sound-absorbing material that can manufacture a composite sound-absorbing material that can obtain a high sound-absorbing effect even when the thickness is reduced.

Brief Description of the Drawings

[0021] [Figure 1] It is a cross-sectional view of the composite sound-absorbing material 1 according to Embodiment 1. [Figure 2] It is a flowchart of the manufacturing method of the composite sound-absorbing material according to Embodiment 1. [Figure 3]This is a diagram illustrating the manufacturing method of the composite sound-absorbing material according to Embodiment 1. [Figure 4] This is a diagram illustrating the composite sound-absorbing material 2 according to Embodiment 2. [Figure 5] This is a flowchart of the manufacturing method for the composite sound-absorbing material according to Embodiment 2. [Figure 6] This is a diagram illustrating the manufacturing method of the composite sound-absorbing material according to Embodiment 2. [Figure 7] This is a diagram illustrating the composite sound-absorbing material 3 according to Embodiment 3. [Figure 8] This is a flowchart of the manufacturing method for the composite sound-absorbing material according to Embodiment 3. [Figure 9] This is a diagram illustrating the manufacturing method of the composite sound-absorbing material according to Embodiment 3. [Figure 10] This is a photograph of the composite sound-absorbing material (sample S) according to the example. [Figure 11] This is a diagram illustrating the melamine foam in the example. [Figure 12] This is a diagram illustrating the nonwoven nanofibers in the examples. [Figure 13] This bar graph shows the pore size of the nonwoven nanofibers in the examples. [Figure 14] This graph shows the measurement results of the normal incidence sound absorption coefficient of the composite sound-absorbing material according to the example. [Modes for carrying out the invention]

[0022] The composite sound-absorbing material and the method for manufacturing the composite sound-absorbing material of the present invention will be described below based on the embodiments shown in the figures. Note that the embodiments described below do not limit the invention as defined in the claims. Furthermore, not all of the elements and their combinations described in each embodiment are necessarily essential as means of solving the problems of the present invention. Also, for components having exactly the same function or substantially the same function, even if their shape differs slightly, common reference numerals will be used in each embodiment, and previously given explanations may be omitted.

[0023] [Embodiment 1] 1. Composite sound-absorbing material Figure 1 is a cross-sectional view of the composite sound-absorbing material 1 according to Embodiment 1. Figure 1 is a cross-sectional view taken from a plane parallel to the lamination direction of the foam layer 10 and the nanofiber layer 20, and the same applies to other cross-sectional views described later. Also, Figure 1 is a schematic diagram and does not accurately represent the ratio of the thicknesses of the foam layer 10 and the nanofiber layer 20. The same applies to the other figures described later.

[0024] The composite sound-absorbing material 1 according to Embodiment 1 comprises a foam layer 10 and a nanofiber layer 20 (see Figure 1). The composite sound-absorbing material 1 may also include other components (for example, a reinforcing layer, a protective layer, etc.). When the composite sound-absorbing material 1 is used as a building material or interior material, the composite sound-absorbing material 1 should be positioned so that the nanofiber layer 20 faces the side where sound is mainly expected to be generated (the side to be absorbed). The basic components of the composite sound-absorbing material 1 will be described below.

[0025] The foam layer 10 has a resin foam 12. The foam layer 10 in the composite sound-absorbing material 1 consists of a resin foam 12. In addition to the resin foam 12, the foam layer 10 may further contain substances (for example, particulate matter or fibrous matter) to improve sound absorption and other physical properties.

[0026] In this specification, "resin foam" refers to a porous structure (sponge-like structure) made of resin. Resin foam is generally formed by adding a foaming agent to a resin material and heating it.

[0027] While the resin foam 12 can be made from various materials, it is preferable that the resin foam 12 be melamine foam (MF). Melamine foam is a resin foam mainly composed of melamine resin. Melamine foam can be formed, for example, by preparing a precursor by reacting melamine monomer and formaldehyde in the presence of a catalyst, and then adding a foaming agent and heating. The melamine foam may also contain resin components other than melamine resin, additives, etc.

[0028] In addition, due to the characteristics of the melamine resin, it is easy for the melamine foam to have a continuous cell structure in which the pores in the structure are continuously connected. The melamine foam with a continuous cell structure is easier to reduce weight due to lower density compared to a resin foam with a closed-cell structure in which the pores in the structure are independent. Further, since sound wave absorption and scattering easily occur in the continuous pores of the melamine foam with a continuous cell structure, the sound absorption performance can be enhanced.

[0029] The resin foam 12 preferably has a thickness within the range of 1 mm to 40 mm. Note that the thickness of the resin foam 12 is not limited to 1 mm to 40 mm, and can be set to any thickness at each stage such as during production, sales, and use. From the viewpoints of actual production, distribution, and use of the composite sound absorbing material 1, it is considered that the thickness of the resin foam 12 can be 0.5 mm to 80 mm.

[0030] Further, the resin foam 12 preferably has a density within the range of 1 kg / m 3 ~20 kg / m 3 Note that the density of the resin foam 12 is not limited to 1 kg / m 3 ~20 kg / m 3 and can be set to any density according to materials (type of resin), production methods, applications, etc. From the viewpoints of materials, production methods, and applications of the composite sound absorbing material 1, it is considered that the density of the resin foam 12 can be 0.5 kg / m 3 ~100 kg / m 3

[0031] The nanofiber layer 20 is laminated on the foam layer 10 and has non-woven nanofibers 22. The nanofiber layer 20 in the composite sound absorbing material 1 is composed of non-woven nanofibers 22. Note that in addition to the non-woven nanofibers 22, the nanofiber layer 20 may further contain substances (for example, particulate substances or fibrous substances) for improving sound absorption properties and physical properties, etc.

[0032] ​In this specification, "nanofiber" refers to an extremely fine fiber having a diameter on the order of nanometers (approximately 1000 nm or less). Furthermore, in this specification, "nonwoven nanofiber" refers to a sheet-like material formed by the intertwining of nanofibers. While nanofibers can be formed by various methods, from the viewpoint of quality, stability, and efficiency, they are preferably formed by electrospinning.

[0033] While nonwoven nanofibers 22 can be made from various materials, it is preferable that the nonwoven nanofibers 22 be made from a thermoplastic polyurethane (TPU) material. A thermoplastic polyurethane material is a material whose main component is thermoplastic polyurethane resin. Note that the thermoplastic polyurethane material may also contain resin components other than thermoplastic polyurethane resin, additives, etc.

[0034] The nonwoven nanofiber 22 has a layering amount (basis weight) of 2 g / m². 2 ~7g / m 2 It is preferable that the pore size is within the range of 0.8 μm to 1.3 μm.

[0035] 2. Method for manufacturing composite sound-absorbing materials Figure 2 is a flowchart of the manufacturing method for the composite sound-absorbing material according to Embodiment 1. Figure 3 is a diagram illustrating the method for manufacturing a composite sound-absorbing material according to Embodiment 1. Figure 3(a) is a cross-sectional view showing the foam layer preparation step S10, and Figure 3(b) is a cross-sectional view showing the nanofiber layer formation step S20.

[0036] Next, a method for manufacturing a composite sound-absorbing material according to Embodiment 1 will be described. The method for manufacturing a composite sound-absorbing material according to Embodiment 1 is a method for manufacturing a composite sound-absorbing material 1 and includes a foam layer preparation step S10 and a nanofiber layer formation step S20 (see Figure 2). The method for manufacturing a composite sound-absorbing material according to Embodiment 1 may also include steps other than those described above (for example, a molding step, a cleaning step, etc.). The basic steps of the method for manufacturing a composite sound-absorbing material according to Embodiment 1 will be described below.

[0037] The foam layer preparation step S10 is a step of preparing a foam layer 10 having a resin foam 12. The method of carrying out the foam layer preparation step S10 is not particularly limited as long as a suitable foam layer 10 can be prepared, and may be carried out, for example, by manufacturing the foam layer 10 or by purchasing it.

[0038] The nanofiber layer formation step S20 is a step in which a nanofiber layer 20 having nonwoven nanofibers 22 is formed using the foam layer 10 as a base material by electrospinning. The nanofiber layer formation step S20 can be carried out by placing the foam layer 10 on a collector (not shown) and performing spinning while applying a voltage between the collector and a nozzle (not shown) that discharges a spinning solution containing nanofiber material.

[0039] 3. Effects of composite sound-absorbing material 1 and the method for manufacturing the composite sound-absorbing material The composite sound-absorbing material 1 according to Embodiment 1 comprises a foam layer 10 having a resin foam 12 and a nanofiber layer 20 laminated on the foam layer 10 and having nonwoven nanofibers 22. Therefore, as shown in the examples described later, it is a composite sound-absorbing material that can obtain a high sound absorption effect even with a reduced thickness compared to conventional sound-absorbing materials.

[0040] Furthermore, according to the composite sound-absorbing material 1 of Embodiment 1, if the resin foam 12 is melamine foam, it is possible to increase the strength and durability.

[0041] Furthermore, according to the composite sound-absorbing material 1 of Embodiment 1, if the nonwoven nanofiber 22 is made of a thermoplastic polyurethane material, it is possible to form a nanofiber layer 20 that has a stable structure and high sound absorption properties.

[0042] Furthermore, according to the composite sound-absorbing material 1 of Embodiment 1, when the thickness of the resin foam 12 is within the range of 1 mm to 40 mm, it is possible to ensure sufficient strength and to exhibit sufficient sound absorption even when it is thin and lightweight.

[0043] Furthermore, according to the composite sound-absorbing material 1 of Embodiment 1, the amount of nonwoven nanofiber 22 laminated is 2 g / m². 2 ~7g / m 2 When within this range, it becomes possible to achieve sufficient sound absorption and to sufficiently suppress the peeling of the nanofiber layer 20.

[0044] Furthermore, according to the composite sound-absorbing material 1 of Embodiment 1, the density of the resin foam 12 is 1 kg / m³ 3 ~20kg / m 3 Within this range, it becomes possible to achieve sufficient sound absorption while also making it sufficiently lightweight.

[0045] Furthermore, according to the composite sound-absorbing material 1 of Embodiment 1, stable sound absorption can be achieved when the average pore size of the nonwoven nanofiber 22 is within the range of 0.8 μm to 1.3 μm.

[0046] The manufacturing method for the composite sound-absorbing material according to Embodiment 1 includes a foam layer preparation step S10 and a nanofiber layer formation step S20, and is a manufacturing method for a composite sound-absorbing material that can produce a composite sound-absorbing material 1 that can obtain a high sound absorption effect even when the thickness is reduced.

[0047] [Embodiment 2] Figure 4 is a diagram illustrating the composite sound-absorbing material 2 according to Embodiment 2. Figure 4(a) is a cross-sectional view of the composite sound-absorbing material 2, and Figure 4(b) is a plan view of the composite sound-absorbing material 2 (viewed from the nanofiber layer 20 side). In Figure 4(b), only the uppermost joint 32 is indicated by a reference numeral. Figure 5 is a flowchart of the manufacturing method for the composite sound-absorbing material according to Embodiment 2. Figure 6 is a diagram illustrating the method for manufacturing a composite sound-absorbing material according to Embodiment 2. Figure 6(a) is a cross-sectional view showing the foam layer preparation step S10, Figure 6(b) is a cross-sectional view showing the bonding material placement step S12, Figure 6(c) is a cross-sectional view showing the nanofiber layer formation step S20, and Figure 6(d) is a cross-sectional view showing the bonding step S30.

[0048] The composite sound-absorbing material 2 according to Embodiment 2 has basically the same configuration as the composite sound-absorbing material 1 according to Embodiment 1, but differs from the composite sound-absorbing material 1 in that it has a bonding material. That is, the composite sound-absorbing material 2 includes a bonding material 30 that bonds the resin foam 12 and the nonwoven nanofiber 22 (see Figure 4).

[0049] The bonding material 30 is a low-melting-point nanofiber made of a low-melting-point resin having a melting point lower than that of the resin foam 12 and the nonwoven nanofiber 22. As the low-melting-point resin, for example, a low-melting-point thermoplastic polyurethane can be used.

[0050] Furthermore, the bonding material 30 partially bonds the foam layer 10 and the nanofiber layer 20. In the composite sound-absorbing material 2, the bonding portion 32, which is part of the bonding material 30, bonds the foam layer 10 and the nanofiber layer 20. The bonding portion 32 is approximately circular (dot-shaped) when viewed from above and is dispersed when the composite sound-absorbing material 2 is viewed from above (see Figure 4(b)). The bonding portion 32 is formed when a part of the bonding material 30 melts due to heating.

[0051] Furthermore, the shape of the joint portion 32 is not limited to a roughly circular shape, but may also be a polygon, cross shape, grid shape, or other shape.

[0052] The composite sound-absorbing material 2 can be manufactured by the manufacturing method for the composite sound-absorbing material according to Embodiment 2. The manufacturing method for the composite sound-absorbing material according to Embodiment 2 basically includes the same steps as the manufacturing method for the composite sound-absorbing material according to Embodiment 1, but differs from the manufacturing method for the composite sound-absorbing material according to Embodiment 1 in that it includes a bonding material placement step and a bonding step.

[0053] The manufacturing method for the composite sound-absorbing material according to Embodiment 2 includes a foam layer preparation step S10, a bonding material placement step S12, a nanofiber layer formation step S20, and a bonding step S30 (see Figure 5). Each step will be described below.

[0054] The foam layer preparation step S10 is substantially the same as the foam layer preparation step S10 in Embodiment 1, so its explanation is omitted (see Figure 6(a)).

[0055] The bonding material placement step S12 is a step in which bonding material 30, which is a low-melting-point nanofiber, is placed (formed) using the electrospinning method on the foam layer 10 as a base material (see Figure 6(b)).

[0056] The nanofiber layer formation step S20 is basically the same as the nanofiber layer formation step S20 in Embodiment 1. In the nanofiber layer formation step S20 in Embodiment 2, the nanofiber layer 20 is laminated onto the foam layer 10 via the bonding material 30 (see Figure 6(c)).

[0057] The bonding step S30 is a step included after the nanofiber layer formation step S20, and is a step in which the resin foam 12 and the nonwoven nanofiber 22 are bonded together (see Figure 6(d)). In the bonding step S30, a portion of the bonding material 30 is heated and then solidified to form the bonded portion 32. The heating of the bonding material 30 can be carried out by methods such as using electromagnetic waves (laser or heat ray, etc.), using a hot press, or using hot air.

[0058] The composite sound-absorbing material 2 according to Embodiment 2 differs from the composite sound-absorbing material 1 in that it has a bonding material, but it comprises a foam layer 10 having a resin foam 12 and a nanofiber layer 20 laminated on the foam layer 10 and having nonwoven nanofibers 22. Therefore, similar to the composite sound-absorbing material 1, it is a composite sound-absorbing material that can obtain a high sound absorption effect even when the thickness is reduced compared to conventional sound-absorbing materials.

[0059] Furthermore, according to the composite sound-absorbing material 2 of Embodiment 2, the composite sound-absorbing material 2 includes a bonding material 30 that joins the resin foam 12 and the nonwoven nanofiber 22, making it possible to suppress the peeling of the nanofiber layer 20 from the foam layer 10.

[0060] Furthermore, according to the composite sound-absorbing material 2 of Embodiment 2, the bonding material 30 is a low-melting-point nanofiber made of a low-melting-point resin having a melting point lower than that of the resin foam 12 and the nonwoven nanofiber 22. Therefore, it can be formed (placed) on the surface of the foam layer 10 in the same way as the nonwoven nanofiber 22, and then melted.

[0061] Furthermore, according to the composite sound-absorbing material 2 of Embodiment 2, since the bonding material 30 partially bonds the foam layer 10 and the nanofiber layer 20, it is possible to avoid hindering sound absorption by membrane vibration of the nanofiber layer 20.

[0062] Since the composite sound-absorbing material 2 according to Embodiment 2 has basically the same configuration as the composite sound-absorbing material 1 according to Embodiment 1, it further possesses the effects of the composite sound-absorbing material 1 that are relevant to that effect.

[0063] The method for manufacturing a composite sound-absorbing material according to Embodiment 2 differs from the method for manufacturing a composite sound-absorbing material according to Embodiment 1 in that it includes a bonding material placement step and a bonding step. However, because it includes a foam layer preparation step S10 and a nanofiber layer formation step S20, it is possible to manufacture a composite sound-absorbing material 2 that can achieve a high sound absorption effect even when the thickness is reduced.

[0064] Furthermore, according to the manufacturing method of the composite sound-absorbing material of Embodiment 2, since the bonding step S30 for bonding the resin foam 12 and the nonwoven fabric-like nanofibers 22 is included after the nanofiber layer formation step S20, it is possible to manufacture a composite sound-absorbing material 2 that can suppress the peeling of the nanofiber layer 20 from the foam layer 10.

[0065] [Embodiment 3] Figure 7 is a diagram illustrating the composite sound-absorbing material 3 according to Embodiment 3. Figure 7(a) is a cross-sectional view of the composite sound-absorbing material 3, and Figure 7(b) is a plan view of the composite sound-absorbing material 3 (viewed from the nanofiber layer 20 side). In Figure 7(b), only the uppermost of the bonding materials 42 is indicated by a reference numeral. Figure 8 is a flowchart of the manufacturing method for the composite sound-absorbing material according to Embodiment 3. Figure 9 is a diagram illustrating the manufacturing method of the composite sound-absorbing material according to Embodiment 3. Figure 9(a) is a cross-sectional view showing the foam layer preparation step S10, Figure 9(b) is a cross-sectional view showing the bonding material placement step S14, and Figures 9(c) to 9(e) are cross-sectional views showing the nanofiber layer attachment step S40.

[0066] The composite sound-absorbing material 3 according to Embodiment 3 has basically the same configuration as the composite sound-absorbing material 1 according to Embodiment 1, but differs from the composite sound-absorbing material 1 in that it has a bonding material. That is, the composite sound-absorbing material 3 includes a bonding material 42 that bonds the resin foam 12 and the nonwoven nanofiber 22 (see Figure 7).

[0067] The bonding material 42 is not particularly limited as long as it can bond the resin foam 12 and the nonwoven nanofiber 22, but for example, it is a solidified adhesive. As the adhesive, for example, emulsion adhesives, solvent adhesives, reaction adhesives, etc., can be used. Alternatively, an adhesive made of a low-melting-point resin having a melting point lower than the melting points of the resin foam 12 and the nonwoven nanofiber 22 (a hot-melt adhesive) can be used.

[0068] Furthermore, the bonding material 42 partially bonds the foam layer 10 and the nanofiber layer 20. When viewed from above, the bonding material 42 is approximately circular (dot-shaped) and is dispersed when the composite sound-absorbing material 3 is viewed from above (see Figure 7(b)). Note that the shape of the bonding material 42 is not limited to approximately circular, but may be polygonal, cross-shaped, grid-shaped, or other shapes.

[0069] The composite sound-absorbing material 3 can be manufactured by the manufacturing method of the composite sound-absorbing material according to Embodiment 3. The manufacturing method of the composite sound-absorbing material according to Embodiment 3 includes a foam layer preparation step S10, a bonding material placement step S14, and a nanofiber layer attachment step S40 (see Figure 8). The manufacturing method of the composite sound-absorbing material according to Embodiment 3 may also include steps other than those described above (for example, a molding step, a cleaning step, etc.). The basic steps of the manufacturing method of the composite sound-absorbing material according to Embodiment 3 will be described below.

[0070] The foam layer preparation step S10 is substantially the same as the foam layer preparation step S10 in Embodiment 1, so its explanation is omitted (see Figure 9(a)).

[0071] The bonding material placement step S14 is a step of placing a bonding material precursor 40 on the surface of the foam layer 10 (see Figure 9(b)). The bonding material precursor 40 solidifies into the bonding material 42, for example, by solvent release or chemical reaction. In cases where the bonding material 42 is a hot melt adhesive, the bonding material precursor 40 may be substantially equivalent to the bonding material 42.

[0072] The nanofiber layer attachment step S40 is a step in which a nanofiber layer 20 having nonwoven nanofibers 22 is attached to the foam layer 10 using a bonding material 42. In the nanofiber layer attachment step S40, first, the nanofiber layer 20, which has been prepared separately from the foam layer 10, is placed on the side of the foam layer 10 where the bonding material precursor 40 is present (see Figures 9(c) and 9(d)).

[0073] Next, the bonding material precursor 40 is solidified to form the bonding material 42, and the nanofiber layer 20 is attached to the foam layer 10 (see Figure 9(e)). The method for converting the bonding material precursor 40 to the bonding material 42 can be arbitrarily determined depending on the type of bonding material precursor 40, and for example, heating, drying, addition of a reactant, or self-reaction of the bonding material precursor can be used. In addition, if the bonding material 42 is a hot-melt adhesive, the nanofiber layer 20 can be attached to the foam layer 10 by heating the bonding material precursor 40, melting it, and then solidifying it.

[0074] The composite sound-absorbing material 3 according to Embodiment 3 differs from the composite sound-absorbing material 1 in that it has a bonding material, but it comprises a foam layer 10 having a resin foam 12 and a nanofiber layer 20 laminated on the foam layer 10 and having nonwoven nanofibers 22. Therefore, similar to the composite sound-absorbing material 1, it is a composite sound-absorbing material that can obtain a high sound absorption effect even when its thickness is reduced compared to conventional sound-absorbing materials.

[0075] Furthermore, according to the composite sound-absorbing material 3 of Embodiment 3, the composite sound-absorbing material 3 includes a bonding material 42 that joins the resin foam 12 and the nonwoven nanofiber 22, making it possible to suppress the peeling of the nanofiber layer 20 from the foam layer 10.

[0076] Furthermore, according to the composite sound-absorbing material 3 of Embodiment 3, since the bonding material 42 partially bonds the foam layer 10 and the nanofiber layer 20, it is possible to avoid hindering sound absorption by membrane vibration of the nanofiber layer 20.

[0077] Since the composite sound-absorbing material 3 according to Embodiment 3 has basically the same configuration as the composite sound-absorbing material 1 according to Embodiment 1, it further possesses the effects of the composite sound-absorbing material 1 that are relevant to that effect.

[0078] The manufacturing method for the composite sound-absorbing material according to Embodiment 3 includes a foam layer preparation step S10 and a nanofiber layer application step S40, and therefore, it is a manufacturing method for a composite sound-absorbing material that can produce a composite sound-absorbing material that can obtain a high sound absorption effect even when the thickness is reduced.

[0079] Furthermore, the manufacturing method for the composite sound-absorbing material according to Embodiment 3 includes a nanofiber layer attachment step S40 in which a nanofiber layer 20 having nonwoven nanofibers 22 is attached to the foam layer 10 using a bonding material 42. This makes it possible to manufacture a composite sound-absorbing material 3 that can suppress the peeling of the nanofiber layer 20 from the foam layer 10.

[0080] [Examples] The inventors of the present invention actually manufactured a composite sound-absorbing material corresponding to the composite sound-absorbing material 1 according to Embodiment 1 described above, and measured its performance. The test content and results related to the composite sound-absorbing material will be described below as examples.

[0081] Figure 10 is a photograph of a composite sound-absorbing material (sample S) according to an example. Figure 11 is a diagram illustrating the melamine foam in the example. Figures 11(a) and 11(b) are SEM images of the melamine foam, and Figure 11(c) is a bar graph showing the pore size of the melamine foam. Figure 12 is a diagram illustrating the nonwoven nanofibers in the example. Figures 12(a) and 12(b) show a lamination amount of 7 g / m². 2 Figure 12(c) shows an SEM image of the nonwoven nanofibers at a layering amount of 7 g / m². 2 This graph shows the average fiber diameter of nonwoven nanofibers under those conditions. Figure 13 is a bar graph showing the pore size of the nonwoven nanofibers in the examples. Figure 13(a) shows a layering amount of 2 g / m². 2 This is a bar graph showing the pore size in the case of 4 g / m², and Figure 13(b) shows the layer thickness as 4 g / m². 2 This is a bar graph showing the pore size in the case of 13(c), where the layer thickness is 7g / m². 2 This is a bar graph showing the pore size in the case of [the specified condition]. Figure 14 is a graph showing the measurement results of the normal incidence sound absorption coefficient of the composite sound-absorbing material according to the example. Figure 14(a) is a graph when the thickness of the melamine foam is 10 mm, and Figure 14(b) is a graph when the thickness of the melamine foam is 20 mm. In the graph of Figure 14, the melamine foam is labeled "MF", and the amount of nonwoven nanofiber laminated is 2 g / m 2 For composite sound-absorbing materials, the designation is "MF+NF(2gsm)," and the amount of nonwoven nanofiber layers is 4g / m². 2 For composite sound-absorbing materials, the designation is "MF+NF(4gsm)," and the amount of nonwoven nanofiber layers is 7g / m². 2 The composite sound-absorbing material is described as "MF+NF(7gsm)". "gsm" stands for "grams per square meter".

[0082] 1. Materials and equipment First, we will describe the materials and equipment used in the examples. Note that general-purpose instruments and equipment will not be described.

[0083] Thermoplastic polyurethane (TPU, melt viscosity (200℃): 10,000 mPa·s to 50,000 mPa·s) was purchased from Kuraray Co., Ltd. Tetrahydrofuran (THF) was purchased from Kanto Chemical Co., Ltd. Dimethylformamide (DMF) was purchased from Fujifilm Wako Pure Chemical Corporation. The petroleum ether (a liquid mixture of pentane and n-hexane) used was purchased from Nacalai Tesque Corporation. Other than the above, standard commercially available reagents were used as raw materials, and were prepared in aqueous solution form as needed.

[0084] For preparing the melamine foam, we used a disc turbine type mixer, the Homomixer MARK II 2.5 model from Primix Corporation. For preparing the melamine foam, we used the YMD-12 (frequency: 2450MHz) microwave irradiation machine from Yamamoto Vinitar Co., Ltd. For the electrospinning method, we used the HVU-30P100 power supply from MEC Corporation. For the electrospinning method, a KDS-100 syringe pump from KD Scientific (USA) was used. The syringe attached to the syringe pump was a standard 25mL syringe. A 20G needle was attached to the tip of the syringe. For measuring sound absorption coefficient, we used the WinZacMTX normal incidence sound absorption coefficient measurement system from Nippon Acoustic Engineering Co., Ltd. The measurement method used was the transfer function method.

[0085] 2. Preparation of resin foam (melamine foam) In the examples, melamine foam was prepared as the resin foam. The melamine foam was manufactured by the method described below.

[0086] First, 2048 parts by weight of melamine monomer and 3622 parts by weight of formaldehyde (aqueous solution, 37 wt%) were placed in a three-necked round-bottom flask equipped with a stirrer, reflux condenser, and thermometer. Sodium hydroxide (aqueous solution, 48 wt%) was added as a basic catalyst to achieve a pH of 9.5, and the reaction was carried out at 95°C for 30 minutes to complete the methylolation reaction. The pH at the end of the reaction was 9.0.

[0087] Subsequently, formic acid (aqueous solution, 76 wt%) was added to adjust the pH to 7.5, and the reaction was carried out at 75°C for 117 minutes. The methylene reaction was terminated when the cloud point (5°C) was confirmed. After the synthesis was complete, the reactants were allowed to cool naturally, and when the temperature had dropped to 60°C, sodium hydroxide (aqueous solution, 48 wt%) was added again to adjust the pH to 9.0. Then, excess water was removed until the solid content was 75 wt%, and the mixture was allowed to cool naturally again to obtain a melamine-formaldehyde reaction precursor (aqueous solution, 75 wt%).

[0088] 100 parts by weight of the melamine-formaldehyde reaction precursor (aqueous solution, 75 wt%) obtained as described above, 1.6 parts by weight of hexamethyldisiloxane, 7.6 parts by weight of petroleum ether, 2.0 parts by weight of sodium dodecylbenzenesulfonate (aqueous solution, 50 wt%), 2.3 parts by weight of formic acid (aqueous solution, 88 wt%), and 1.6 parts by weight of sodium formate (aqueous solution, 50 wt%) were placed in a disc turbine mixer and stirred at a rotation speed of 3000 rpm for 1 minute to obtain a mixed solution.

[0089] The resulting mixed solution was poured into a polyethylene container and irradiated with microwaves at 1.32 kW for 300 seconds using a microwave irradiator to induce foaming. The foamed mixed solution was then demolded and completely cured by heating at 250°C for 20 minutes to obtain melamine foam. The resulting melamine foam was white and had a density of 10 kg / m³. 3 It was a resilient foam. The above melamine foam was shaped to prepare melamine foam with a thickness of 10 mm and melamine foam with a thickness of 20 mm.

[0090] 3. Manufacturing of composite sound-absorbing materials In the example, a sample of composite sound-absorbing material was manufactured by using the melamine foam prepared as described above as the foam layer and laminating nonwoven nanofibers (nanofiber layer) made of thermoplastic polyurethane by electrospinning (see Figure 10).

[0091] The spinning solution used in the electrospinning method was prepared by dissolving thermoplastic polyurethane (TPU) in a THF:DMF = 1:3 (weight ratio) solution to a concentration of 15 wt%. The spinning solution was then placed in a syringe, and the electrospinning method was carried out by applying a voltage between the spinning solution in the syringe and the collector. In the example, melamine foam was placed on the surface of the collector, and the electrospinning method was performed to directly form nonwoven nanofibers on the melamine foam.

[0092] In the electrospinning method described in the example, the spinning solution discharge rate was set to 1 mL / h, and the needle-collector voltage was set to 10 kV to 15 kV. The needle-collector distance (TCD) was set to 200 mm. The electrospinning method was carried out in air at a temperature of approximately 23°C and a relative humidity of 40% or less.

[0093] Using the method described above, a composite sound-absorbing material was manufactured by laminating a nanofiber layer onto a foam layer (10 mm and 20 mm thick). The amount of nonwoven nanofiber lamination was 2 g / m². 2 4g / m 2 and 7g / m 2 These were the three types.

[0094] The melamine foam in the examples was porous, with pore sizes concentrated in the range of 60 μm to 75 μm (see Figure 11).

[0095] The nonwoven nanofibers in the examples have a homogeneous nonwoven fabric structure, and the lamination amount is 7 g / m². 2 In this case, the average fiber diameter was 274 ± 121 nm (see Figure 12). Since there was no significant difference in the appearance or average fiber diameter of the nanofibers depending on the layering amount, the layering amount was 7 g / m². 2 A representative SEM image for this case is shown. Furthermore, the pore size of the nanofiber nonwoven fabric varied slightly depending on the layer thickness, with a tendency for the pore size to decrease as the layer thickness increased, but overall it was concentrated within the range of 0.8 μm to 1.3 μm (see Figure 13).

[0096] 4. Measurement of sound absorption coefficient Next, the sound absorption coefficient of the manufactured composite sound-absorbing material was measured. The sound absorption coefficient was evaluated by measuring the normal incidence sound absorption coefficient when sound waves were irradiated from the nanofiber layer side.

[0097] As a result, it was confirmed that laminating nonwoven nanofibers (nanofiber layer) resulted in superior sound absorption over a wide frequency range compared to using melamine foam (foam layer) alone (see Figure 14).

[0098] Furthermore, it was confirmed that the absorption characteristics tend to shift to higher frequencies as the amount of nonwoven nanofiber layering increases. In addition, it was confirmed that even when the melamine foam thickness in the composite sound-absorbing material is 10 mm, it can exhibit sound absorption performance close to that of a 20 mm thickness. From the results obtained, it is considered that the membrane vibration of the nonwoven nanofiber contributes significantly to the sound absorption performance of the composite sound-absorbing material.

[0099] Although the present invention has been described above based on the embodiments described above, the present invention is not limited to the embodiments described above. It can be implemented in various forms without departing from the spirit of the invention, and for example, the following modifications are also possible.

[0100] (1) The shape, size, position, etc. of the components in the present invention are not limited to those shown in the descriptions of the embodiments and drawings above, and can be changed as appropriate as long as the effects of the present invention are not impaired. Also, the drawings are schematic diagrams, and the shapes, etc. of the components in each drawing are not necessarily accurate.

[0101] (2) In the above embodiments, the resin foam 12 is preferably melamine foam, but the present invention is not limited thereto. The resin foam may be mainly composed of resins other than melamine resin (for example, polyurethane, polystyrene, phenolic resin, ethylene vinyl acetate, polyethylene).

[0102] (3) In the above embodiments, it was preferred that the nonwoven nanofibers 22 be made of a thermoplastic polyurethane resin, but the present invention is not limited thereto. The nonwoven nanofibers may be mainly composed of resins other than thermoplastic polyurethane resins (for example, polyamide, polypropylene, polyvinyl acetate, polyethylene terephthalate, polyurethane, polyacrylonitrile, polyetherimide, polyvinyl alcohol, polyvinylidene fluoride, chitosan). Furthermore, the nonwoven nanofibers may be mainly composed of easily decomposable resins (for example, biodegradable resins such as polylactic acid or polycaprolactone) considering disposal and recycling after use.

[0103] (4) In the above embodiment 2, the bonding material 30 was placed (formed) over the entire surface of the foam layer 10, but the present invention is not limited thereto. The bonding material may be placed only in the part where the joint should be formed or around thereto. Furthermore, the bonding material does not have to be low-melting-point nanofibers, nor does it have to be low-melting-point resin, as long as it can bond the resin foam and the nonwoven fabric-like nanofibers.

[0104] (5) In the above embodiment 3, the bonding material placement step S14 is performed before the nanofiber layer attachment step S40, but the present invention is not limited thereto. The bonding material placement step may be performed as part of the nanofiber layer attachment step. For example, after the foam layer and the nanofiber layer are superimposed, it is also possible to impregnate the nanofiber layer with a liquid bonding material from the nanofiber layer side. [Explanation of Symbols]

[0105] 1,2,3...Composite sound-absorbing material, 10...Foam layer, 12...Resin foam, 20...Nanofiber layer, 22...Nonwoven nanofiber, 30,42...Bonding material, 32...Bond, 40...Bonding material precursor

Claims

1. A foam layer having a resin foam, A composite sound-absorbing material characterized by comprising a nanofiber layer laminated on the foam layer and having nonwoven nanofibers.

2. The composite sound-absorbing material according to claim 1, characterized in that the resin foam is melamine foam.

3. The composite sound-absorbing material according to claim 1, characterized in that the nonwoven nanofiber is made of a thermoplastic polyurethane material.

4. The composite sound-absorbing material according to claim 1, further comprising a bonding material for bonding the resin foam and the nonwoven nanofiber.

5. The composite sound-absorbing material according to claim 4, characterized in that the bonding material is a low-melting-point nanofiber made of a low-melting-point resin having a melting point lower than the melting point of the resin foam and the nonwoven nanofiber.

6. The composite sound-absorbing material according to claim 4, characterized in that the bonding material partially bonds the foam layer and the nanofiber layer.

7. The composite sound-absorbing material according to claim 1, characterized in that the resin foam has a thickness in the range of 1 mm to 40 mm.

8. The aforementioned nonwoven nanofiber has a layering amount of 2 g / m². ２ ~7g / m ２ The composite sound-absorbing material according to claim 1, characterized in that it is within the range.

9. The aforementioned resin foam has a density of 1 kg / m³ ３ ~20 kg / m ３ The composite sound-absorbing material according to claim 1, characterized in that it is within the range.

10. The composite sound-absorbing material according to claim 1, characterized in that the nonwoven nanofiber has an average pore diameter in the range of 0.8 μm to 1.3 μm.

11. A foam layer preparation step for preparing a foam layer having a resin foam, A method for producing a composite sound-absorbing material, characterized by comprising a nanofiber layer formation step of forming a nanofiber layer having nonwoven nanofibers using an electrospinning method with the foam layer as a base material.

12. The method for manufacturing a composite sound-absorbing material according to claim 11, further comprising a bonding step of bonding the resin foam and the nonwoven nanofibers after the nanofiber layer formation step.

13. A foam layer preparation step for preparing a foam layer having a resin foam, A method for manufacturing a composite sound-absorbing material, characterized by including a nanofiber layer attachment step of attaching a nanofiber layer having nonwoven nanofibers to the foam layer using a bonding material.

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