Sound absorption material

Abstract

To provide a sound absorption material that improves a sound absorption coefficient by suppressing thickness reduction after bonding.SOLUTION: A sound absorption material comprises a surface layer and a base material layer, where the base layer consists of multiple types of fibers including water-repellent fibers. Incorporating water-repellent fibers into the base material of the sound absorption material can suppress excessive contraction of inter-fiber voids during bonding process between fibers in the manufacturing process of the sound absorption material. This can suppress reduction in thickness of the sound absorption material after bonding. The sound absorption material of the embodiment containing water-repellent fibers exhibits an improved sound absorption coefficient over a wider frequency range compared to the sound absorption material of comparative examples that do not contain the water-repellent fibers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present technology relates to a sound-absorbing material, and more particularly to a sound-absorbing material that is suppressed from reducing in thickness. [Background technology]

[0002] Conventionally, techniques for imparting water repellency to sound absorbing materials have been known.

[0003] For example, Patent Document 1 below discloses a technology for imparting water repellency to mats and the like, taking into consideration that when moisture gets into the sound-absorbing layer of mats for automobiles or entranceways, it impairs the sound-absorbing performance, damages the material on the bottom where the moisture has seeped in, and promotes the growth of mold and other bacteria due to retained humidity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-31404 Summary of the Invention [Problem to be solved by the invention]

[0005] The main purpose of this technology is to improve the sound absorption coefficient of the sound-absorbing material by suppressing the reduction in thickness of the sound-absorbing material after bonding. [Means for solving the problem]

[0006] As a result of extensive research, the inventors have discovered that by incorporating water-repellent fibers into the base material of the sound-absorbing material, it is possible to prevent excessive shrinkage of the gaps between the fibers during the process of bonding the fibers together in the manufacturing process of the sound-absorbing material, and to prevent a reduction in the thickness of the sound-absorbing material after bonding.

[0007] That is, the present technology provides a sound-absorbing material having a surface layer and a base layer, the base layer being made of a plurality of types of fibers including water-repellent fibers. In the sound-absorbing material of this technology, the density of the base material layer is 50 kg / m3 It can be adjusted as follows: In the sound-absorbing material according to the present technology, the plurality of fibers may include hollow fibers, and the water-repellent fibers may be hollow fibers. In the sound-absorbing material of the present technology, the material constituting the surface layer and the material constituting the base material layer may be the same. The sound-absorbing material of this technology has a surface air permeability of 35cc / cm 2 / sec or more. [Brief explanation of the drawings]

[0008] [Figure 1] These are the measurement results of the sound absorption coefficient of a sound absorbing material that contains water-repellent fibers in the base material and a sound absorbing material that does not contain water-repellent fibers. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments for implementing the present technology will be described below. The embodiments described below are examples of typical embodiments of the present technology, and any of the embodiments can be combined. Furthermore, the scope of the present technology is not to be interpreted narrowly by these embodiments.

[0010] [Sound absorbing material] <Base material layer> The base layer of the sound-absorbing material of the present technology is made of multiple types of fibers including water-repellent fibers.

[0011] Sound-absorbing materials used in interior materials such as the sides and ceilings of automobiles, which are not expected to be stepped on by people, are less likely to become contaminated with moisture than sound-absorbing materials used in mats, which are prone to becoming contaminated with moisture when stepped on by people, etc. For this reason, when imparting water repellency to sound-absorbing materials used in interior materials, a water-repellent agent is often applied to the surface of the sound-absorbing material.

[0012] In contrast, the sound-absorbing material of the present technology reduces the entanglement of fibers by blending water-repellent fibers into the fibers of a base layer formed by bonding multiple fibers, rather than on the surface of the sound-absorbing material. This increases the contact angle when the fused resin comes into contact with the water-repellent fibers during the process of bonding the fibers together in the manufacturing process of the sound-absorbing material. It also reduces the contact area when the fused resin comes into contact with the water-repellent fibers. This prevents excessive shrinkage of the gaps between the fibers. As a result, the thickness of the sound-absorbing material after bonding is suppressed, and the sound absorption coefficient of the resulting sound-absorbing material is improved.

[0013] In this specification, the term "interior materials" refers to components that constitute areas of a specific object (such as an automobile) that are not expected to be stepped on by people. Examples of interior materials include the ceiling, instrument panel, door panel, motor compartment, trunk, etc. of an internal combustion engine automobile or an electric automobile.

[0014] Furthermore, the term "water-repellent fiber" refers to a fiber that has the ability to repel liquids such as water on its surface. Examples of water-repellent fibers include fibers that have been treated to be water-repellent and fibers made of materials that themselves have water-repellent properties.

[0015] When the water-repellent fiber is a fiber that has been treated to be water-repellent, the water-repellent treatment can be performed by applying any water-repellent treatment, such as silicone or fluororesin treatment, to the surface of the fiber in accordance with the characteristics of the fiber, thereby making it possible to obtain a water-repellent fiber in a suitable manner.

[0016] The water-repellent fiber that can be used in the sound-absorbing material of the present technology can be any fiber that can be used for interior materials. For example, PET (polyethylene terephthalate) can be preferably used. When considering recycling of the sound-absorbing material, PET can be preferably used.

[0017] When using PET as a water-repellent fiber that can be used in the sound-absorbing material of this technology, as mentioned above, water-repellent PET fiber can be obtained by applying any water-repellent treatment such as silicone or fluororesin treatment to the surface of the PET fiber.

[0018] The fineness of the water-repellent fiber that can be used in the sound-absorbing material of the present technology can be any fineness that can be used in interior materials. For example, it can be adjusted to a range of less than 10 denier, less than 9 denier, less than 8 denier, etc. Furthermore, there is no particular lower limit for the fineness of the water-repellent fiber, and it can be adjusted appropriately depending on the sound absorption coefficient required for the sound-absorbing material.

[0019] In the sound-absorbing material of the present technology, by adjusting the proportion of water-repellent fibers among the multiple types of fibers that make up the base material layer, it is possible to ensure adhesion between the fibers during the process of bonding the fibers while preventing excessive shrinkage of the gaps between the fibers.

[0020] The ratio of the water-repellent fibers to all the fibers constituting the base material layer can be adjusted, for example, to 1% or more, 5% or more, 10% or more, depending on the density of the base material of the sound-absorbing material to be manufactured. The upper limit of the ratio of the water-repellent fibers to all the fibers can also be adjusted, for example, to 20% or less, 15% or less, depending on the above.

[0021] The base layer of the sound-absorbing material of the present technology is made of multiple types of fibers, such as water-repellent or non-water-repellent fibers, fibers of different shapes, fibers of different fineness, fibers with binder properties or non-binder properties, fibers of different materials or properties, or fibers with a combination of these properties. These multiple types of fibers each have a different resonance frequency, so by combining them it is possible to improve the sound absorption coefficient over a wide frequency range.

[0022] Here, "material" refers to the material that constitutes an object (fiber), and "quality" refers to the properties (tensile strength, heat resistance, etc.) of the material that constitutes an object (fiber).

[0023] Examples of fibers with different shapes include fibers that do not have a hollow space in the fiber and hollow fibers that have a hollow space in the fiber.

[0024] When the plurality of fibers constituting the base layer of the sound-absorbing material according to the present technology include hollow fibers, the density of the base layer can be made low relative to the thickness of the base layer. In this case, it is preferable that the shape of the hollow fibers used has a hollow cavity along the longitudinal direction of the fibers, from the viewpoint of maintaining the shape and density of the hollow fibers.

[0025] The water-repellent fibers used in the sound-absorbing material of the present technology may be hollow fibers. In this case, the water-repellent properties reduce the tendency for the fibers to become entangled, thereby making it possible to maintain the shape of the hollow fibers in a suitable manner.

[0026] In addition, cases in which the multiple fibers constituting the base layer of the sound-absorbing material of the present technology include hollow fibers include cases in which the fibers include water-repellent fibers and hollow fibers different from the water-repellent fibers, cases in which the water-repellent fibers are hollow fibers, and cases in which the water-repellent fibers are hollow fibers and further include hollow fibers different from the water-repellent fibers.

[0027] In the sound-absorbing material of the present technology, the multiple fibers constituting the base layer may include at least two or more types of fibers with different finenesses. Since two or more types of fibers with different finenesses each have a different resonance frequency, combining these fibers can improve the sound absorption coefficient over a wide frequency range and improve the sound absorption coefficient for a target frequency.

[0028] In this case, for example, fibers having a different fineness from that of the water-repellent fibers may be used, or fibers having a different fineness from that of the fibers other than the water-repellent fibers that constitute the base layer may be used.

[0029] In the sound-absorbing material according to the present technology, the plurality of fibers constituting the base layer may include binder fibers that act as binders to bond the fibers constituting the base layer together in a process of bonding the fibers together.

[0030] The binder fiber may be, for example, a fiber having a core-sheath structure in which a high-melting point component is the core and a low-melting point component is the sheath, or may be a fiber made of a material or substance having a lower melting point than the other fibers constituting the base material layer.

[0031] When PET is used as the water-repellent fiber that can be used in the sound-absorbing material of this technology, the binder fiber is not particularly limited as long as it can bond the fibers used together. For example, the recyclability of the sound-absorbing material can be improved by using fibers made of low-melting-point PET (low-melting-point polyethylene terephthalate), which is the same material as the PET that is the material of the water-repellent fiber but has a lower melting point, as the binder fiber.

[0032] The base layer of the sound-absorbing material of the present technology is formed by combining water-repellent fibers with the above-mentioned multiple types of fibers, and in the process of bonding the fibers together during the manufacturing process of the sound-absorbing material, the contact angle when the resin derived from the fused binder resin comes into contact with the water-repellent fibers is increased and the contact area is reduced, thereby preventing excessive shrinkage of the gaps between the fibers. As a result, the density of the base layer can be increased to, for example, 50 kg / m 3 Below 20kg / m 3 Below 10kg / m 3 It can be adjusted as follows:

[0033] As described above, the multiple types of fibers constituting the base layer of the sound-absorbing material of the present technology can be made of fibers of different materials, but they can also be made of a single material. When the base layer of the sound-absorbing material of the present technology is made of a single material, recyclability can be improved. For example, when PET is used as a water-repellent fiber that can be used in the sound-absorbing material of the present technology, recyclability can be improved by using PET as the material for the other fibers constituting the base layer.

[0034] The fineness of the multiple types of fibers that can be used in the sound-absorbing material of the present technology can be any fineness that can be used for interior materials, similar to the fineness of the water-repellent fiber described above. For example, the fineness can be adjusted to a range of less than 10 denier, less than 9 denier, less than 8 denier, etc. Furthermore, the lower limit of the fineness of the water-repellent fiber is not particularly limited and can be adjusted appropriately depending on the sound absorption coefficient required for the sound-absorbing material. Furthermore, as described above, two or more types of fibers with different finenesses within the above range can be selected to have different resonant frequencies.

[0035] As mentioned above, the base layer of the sound-absorbing material of the present technology is intended to prevent excessive shrinkage of the interfiber voids. Therefore, by not using processes involving compression, such as needle punching or heat rolling, in the manufacturing process, the thickness of the sound-absorbing material can be maintained at an appropriate level.

[0036] <Surface layer> The sound-absorbing material of the present technology may further have a surface layer. In this case, by having the surface layer with a different flexibility from the base layer, the sound absorption coefficient of the entire sound-absorbing material can be improved by a spring mass model in which the vibration of the surface layer, which functions as a vibration layer, is suppressed by the base layer, which functions as a vibration-damping layer.

[0037] Generally, the sound absorption coefficient for a target frequency can be adjusted by adjusting the air permeability of the surface layer. For example, if the surface layer is 20cc / cm 2 When the surface layer has a low air permeability of 1 / sec or less, the sound absorption coefficient in the mid-frequency range of 1,000 to 2,500 Hz is improved by the spring mass model. On the other hand, when the surface layer has a low air permeability, sounds with shorter wavelengths in the range higher than the mid-frequency range (for example, 8,000 to 10,000 Hz) are reflected by the surface of the surface layer and do not penetrate into the sound-absorbing material, which may result in a decrease in the sound absorption coefficient in the high-frequency range.

[0038] As mentioned above, the sound-absorbing material of this technology reduces the tendency for fibers to become entangled by mixing water-repellent fibers into the fibers that make up the base layer, preventing excessive shrinkage of the gaps between the fibers and preventing a reduction in the thickness of the sound-absorbing material after bonding, thereby improving the sound absorption rate of the sound-absorbing material.

[0039] Therefore, when the sound-absorbing material of the present technology is used as the base layer of a sound-absorbing material having a surface layer and a base layer, the air permeability of the surface layer is set higher than the above-mentioned low air permeability, and adjusted so that sounds with short wavelengths in the high-frequency range penetrate into the sound-absorbing material, and even if the improvement rate of the sound absorption coefficient by the surface layer in the mid-frequency range is suppressed, the target sound absorption coefficient can be ensured in the mid-frequency range. This makes it possible to ensure the target sound absorption coefficient in both the mid-frequency and high-frequency ranges.

[0040] When the surface layer has a higher air permeability than the low air permeability, the air permeability is, for example, 35 cc / cm 2 / sec or more, 40cc / cm 2 / sec or more, 45cc / cm 2 In this case, the upper limit of the air permeability is not particularly limited, but for example, it is 80 cc / cm 2 / sec or less, 75cc / cm 2 / sec or less, 70cc / cm 2 Can be adjusted below / sec.

[0041] When the air permeability of the surface layer is adjusted to the above range, it is not necessary to add an air permeability adjuster such as pulp to the material constituting the surface layer. In this case, for example, by forming the surface layer from a single material, recyclability can be improved.

[0042] When the air permeability of the surface layer is adjusted within the above range, there is no need to use a heated roll to compress the surface by applying heat during the production of the sound-absorbing material, which reduces the occurrence of rustling noise in the surface layer that would otherwise be caused by the heated roll.

[0043] In addition, by eliminating the need for a heat roll, the surface layer can be softened, which improves the shape-following ability of the sound-absorbing material, and is expected to improve the ease of assembling parts.

[0044] When the sound-absorbing material of the present technology has a surface layer, recyclability can be improved by using the same material for the surface layer and the base layer. For example, if the base layer is made of multiple types of fibers made of PET, recyclability can be improved by using PET for the surface layer as well.

[0045] <Other layers> The sound-absorbing material of the present technology may also include layers other than the above-mentioned layers as needed, as long as the desired physical properties are not significantly impaired.

[0046] As described above, the sound-absorbing material of the present technology is suitable for use in interior materials that are not intended to be stepped on by people, etc. When considering automobiles as interior materials, for example, in recent years, electric vehicles powered by motors have been increasing in addition to engine-powered automobiles.

[0047] In the case of electric vehicles, in addition to absorbing road noise and wind noise, which are sounds in the mid-frequency band of 1,000 to 2,500 Hz, sound absorption is also required for motor noise, which is sounds in the high-frequency band of 8,000 to 10,000 Hz. As mentioned above, the sound-absorbing material of this technology can ensure the target sound absorption coefficient in both the mid-frequency and high-frequency ranges, so it can also be used suitably as an interior material for electric vehicles.

[0048] The present technology can also be configured as follows. [1] A surface layer and a substrate layer, The base layer is a sound-absorbing material made of multiple types of fibers including water-repellent fibers. [2] A substrate layer made of multiple types of fibers including water-repellent fibers, A sound-absorbing material, wherein the water-repellent fibers are hollow fibers. [3] The density of the base material layer is 50 kg / m 3 The sound-absorbing material according to [1] or [2] below. [4] The sound-absorbing material according to any one of [1] to [3], wherein the fineness of the water-repellent fibers is less than 10 denier. [5] The sound-absorbing material according to any one of [1] to [4], wherein the plurality of fibers include hollow fibers. [6] The sound-absorbing material according to any one of [1] and [3] to [5], wherein the water-repellent fibers are hollow fibers. [7] The sound-absorbing material according to any one of [1] to [6], wherein the plurality of types of fibers include at least two or more types of fibers with different finenesses. [8] The sound-absorbing material according to any one of [1] and [3] to [7], wherein the surface layer and the base layer are made of the same material. [9] The air permeability of the surface layer is 35cc / cm 2 / sec or more.

[10] The sound-absorbing material according to any one of [1] to [9], which is for use as an interior material. [Example]

[0049] The present technology will be described in more detail below using examples, but the present technology is not limited to the contents of the examples shown below.

[0050] Example <Manufacturing of sound-absorbing materials related to this technology> The fibers shown below were uniformly mixed and then carded to obtain the surface layer.

[0051] ◆Surface layer (1) PET fiber : PET fiber / Fineness less than 10 denier / Melting point 260℃ (2) Binder fiber : Low melting point PET fiber / Fineness less than 10 denier / Melting point 120℃

[0052] On one side of the obtained surface layer, several types of fibers shown below were layered while being mixed with air to obtain a laminated structure of the surface layer and base layer. The fibers were then bonded together using hot air at 170 to 180°C to obtain a sound-absorbing material according to the present technology. The thickness of the base layer of the obtained sound-absorbing material was 29 mm.

[0053] ◆Base material layer (1) Water-repellent hollow fiber : PET fiber / Silicone processing / Fineness less than 10 denier / Melting point 260℃ (2) Hollow fiber : PET fiber / Fineness less than 10 denier / Melting point 260℃ (3) Fibers with no hollows : PET fiber / Fineness less than 10 denier / Melting point 260℃ (4) Binder fiber : Low melting point PET fiber / Fineness less than 10 denier / Melting point 120℃

[0054] Comparative Example <Production of a sound-absorbing material according to a comparative example> A base layer was laminated on one side of a surface layer manufactured under the same conditions as those of the Examples, while agitating the following types of fibers with air, to obtain a sound-absorbing material according to a comparative example. Note that the Examples and Comparative Examples were identical in all conditions except for the types of fibers used in the base layer. Specifically, the Comparative Example replaced the water-repellent hollow fibers in the Examples with hollow fibers of the same fiber type (fineness) that had not been treated for water repellency, and the total mass percentage of the water-repellent hollow fibers and the hollow fibers (that had not been treated for water repellency) in the Examples was set to the mass percentage of the hollow fibers (that had not been treated for water repellency) in the Comparative Example. Note that the fibers without hollow cores and the binder fibers in the Examples and Comparative Examples were identical in fiber type (fineness) and mass percentage of each fiber type. The thickness of the base layer of the sound-absorbing material obtained as the Comparative Example was 21 mm.

[0055] ◆Base material layer (1) Hollow fiber : PET fiber / Fineness less than 10 denier / Melting point 260℃ (2) Fibers with no hollows : PET fiber / Fineness less than 10 denier / Melting point 260℃ (3) Binder fibers : Low melting point PET fiber / Fineness less than 10 denier / Melting point 120℃

[0056] From the above results, it is thought that in the sound-absorbing material of the example using water-repellent fibers, the process of bonding the fibers together using hot air increases the contact angle when the resin derived from the fused binder fibers comes into contact with the water-repellent fibers, and reduces the contact area, thereby preventing excessive shrinkage of the gaps between the fibers, thereby ensuring the thickness of the base material layer.

[0057] <Sound absorption coefficient evaluation> The sound absorption coefficients of the sound-absorbing materials according to the above examples and the sound-absorbing materials according to the comparative examples were measured in accordance with JISA 1409. The measurement results are shown in the graph in Figure 1. In the graph in Figure 1, the horizontal axis represents frequency and the vertical axis represents sound absorption coefficient.

[0058] From the results in FIG. 1, it can be seen that the sound absorbing material of the example using the water-repellent fiber has an improved sound absorption coefficient over a wide frequency range compared to the sound absorbing material of the comparative example.

Claims

1. A surface layer and a base layer, The base layer is a sound-absorbing material made of multiple types of fibers including water-repellent fibers.

2. The density of the substrate layer is 50 kg / m ３ 2. The sound-absorbing material according to claim 1, wherein:

3. The sound-absorbing material of claim 1 , wherein the plurality of fibers include hollow fibers, and the water-repellent fibers are hollow fibers.

4. The sound-absorbing material according to claim 1 , wherein the surface layer and the base layer are made of the same material.

5. The air permeability of the surface layer is 35 cc / cm ２ The sound-absorbing material according to claim 1, wherein the sound-absorbing material has a vibration damping ratio of 1 / sec or more.

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