Porous sound-absorbing material, method for manufacturing the same, and sound-absorbing method

Abstract

To provide a porous sound absorbing material capable of obtaining an excellent sound absorbing coefficient at 1,000 Hz, and a sound absorbing method using the porous sound absorbing material or the like.SOLUTION: A porous sound absorbing material includes a low-density region and a high-density region, in which the low-density region and the high-density region contain an ethylene propylene diene rubber, apparent density of the low-density region is more than 0 kg / m3 and is 100 kg / m3 or less and apparent density of the high-density region is more than 100 kg / m3 and is 400 kg / m3 or less. A sound absorbing method includes a sound absorbing step to absorb sound by using the porous sound absorbing material, and in the sound absorbing step, the high-density region of the porous sound absorbing material is positioned closer to a side of a sound source than the low-density region.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a porous sound-absorbing material, a method for manufacturing the same, a sound-absorbing method, and the like.

Background Art

[0002] Conventionally, as sound-absorbing materials, fibrous materials such as glass wool, and foam materials such as polystyrene foam, polyurethane foam, and polyethylene foam have been used ( "foam" is also referred to as "foamed body"). For example, as a sound-absorbing material, it is known to use a propylene-based resin containing a propylene-ethylene copolymer and having a melting start temperature in the range of 60 to 100°C (see, for example, Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the audible frequency range of humans is generally said to be from about 20 Hz to about 20,000 Hz, although there are individual differences. In order to reduce unpleasant sounds felt by humans in buildings, various vehicles, airplanes, etc. (especially so-called road noise that enters the interior of a moving automobile), in recent years, it has been required to absorb sounds in the low-frequency range (for example, frequencies of 1000 Hz or less) with a sound-absorbing material. In order to enhance the sound absorption characteristics in the low-frequency range, it is effective to increase the thickness of the sound-absorbing material or increase the weight of the sound-absorbing material (increase the mass density of the sound-absorbing material). However, these methods have the problem that the use and / or the place of use of the sound-absorbing material are restricted. Therefore, it is required that the sound-absorbing material maintains sufficient sound absorption characteristics even when the sound-absorbing material is thinned or lightened by improving the sound absorption characteristics.

[0005] One aspect of the present invention aims to provide a porous sound-absorbing material capable of obtaining excellent sound absorption rate at 1000 Hz. Another aspect of the present invention aims to provide a sound absorption method using the porous sound-absorbing material. Another aspect of the present invention aims to provide a manufacturing method of a porous sound-absorbing material capable of obtaining the porous sound-absorbing material.

Means for Solving the Problems

[0006] The inventor focused on a porous sound-absorbing material having a low-density region and a high-density region with a specific apparent density, and found that by using the porous sound-absorbing material in a state where the high-density region is located on the sound source side with respect to the low-density region, an excellent sound absorption rate can be obtained at 1000 Hz.

[0007] One aspect of the present invention relates to a porous sound-absorbing material comprising a low-density region and a high-density region, wherein the low-density region and the high-density region contain ethylene-propylene-diene rubber, and the apparent density of the low-density region is more than 0 kg / m 3 and less than or equal to 100 kg / m 3 and the apparent density of the high-density region is more than 100 kg / m 3 and less than or equal to 400 kg / m 3 .

[0008] Another aspect of the present invention relates to a sound absorption method comprising a sound absorption step of performing sound absorption using the above-described porous sound-absorbing material, wherein in the sound absorption step, the high-density region of the porous sound-absorbing material is located on the sound source side with respect to the low-density region.

[0009] Another aspect of the present invention relates to a manufacturing method of the above-described porous sound-absorbing material, comprising a step of obtaining the low-density region and the high-density region by foaming a first unfoamed body and a second unfoamed body having different compositions and laminated on each other, wherein the first unfoamed body and the second unfoamed body contain ethylene-propylene-diene rubber and a foaming agent.

[0010] According to the above-mentioned porous sound-absorbing material, its manufacturing method, and the sound-absorbing method, an excellent sound absorption rate can be obtained at 1000 Hz. Further, since excellent sound absorption characteristics are obtained, sufficient sound absorption characteristics can be maintained even when the sound-absorbing material is thinned or lightened.

Effects of the Invention

[0011] According to one aspect of the present invention, it is possible to provide a porous sound-absorbing material capable of obtaining an excellent sound absorption rate at 1000 Hz. According to another aspect of the present invention, it is possible to provide a sound-absorbing method using the porous sound-absorbing material. According to another aspect of the present invention, it is possible to provide a manufacturing method of a porous sound-absorbing material capable of obtaining the porous sound-absorbing material.

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made and implemented within the scope of the gist thereof.

[0013] In this specification, the symbol "~" indicating a numerical range means that it is from the numerical value described immediately before "~" to the numerical value described immediately after "~". For example, when described as "numerical value x~numerical value y" (where x and y are numerical values), it means the range of "x or more and y or less". "x or more" in a numerical range means x and the range exceeding x. "y or less" in a numerical range means y and the range less than y. In the numerical ranges described step by step in this specification, the upper limit value or lower limit value of a numerical range at a certain step can be arbitrarily combined with the upper limit value or lower limit value of a numerical range at another step. In the numerical ranges described in this specification, the upper limit value or lower limit value of the numerical range may be replaced with the value shown in the examples. "A or B" means that either A or B may be included, or both may be included. The materials exemplified in this specification may be used alone or in combination of two or more. In this specification, the usage amount of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified.

[0014] The porous sound-absorbing material according to this embodiment includes a low-density region and a high-density region. The low-density region and the high-density region contain ethylene-propylene-diene rubber, and the apparent density of the low-density region exceeds 0 kg / m 3 and is 100 kg / m or less, and the apparent density of the high-density region exceeds 100 kg / m 3 and is 400 kg / m or less. 3 and is 400 kg / m or less. 3

[0015] According to the porous sound-absorbing material (low-frequency sound-absorbing material) according to this embodiment, by using the porous sound-absorbing material in a state where the high-density region is located on the sound source side with respect to the low-density region, it is possible to obtain excellent sound-absorbing characteristics (sound absorption) in the low-frequency region, and an excellent sound absorption rate at 1000 Hz can be obtained. According to the porous sound-absorbing material according to this embodiment, a sound absorption rate of 0.40 or more (preferably 0.60 or more) at 1000 Hz measured in accordance with JIS A 1405-2 can be obtained.

[0016] ​ According to the porous sound-absorbing material according to this embodiment, it is also possible to obtain excellent sound-absorbing characteristics in the frequency range of 2000 Hz or less. For example, an excellent sound absorption rate can be obtained at 2000 Hz. According to the porous sound-absorbing material according to this embodiment, a sound absorption rate of 0.40 or more (preferably 0.60 or more) can be obtained as the sound absorption rate at 2000 Hz measured in accordance with JIS A 1405-2.

[0017] In the porous sound-absorbing material according to this embodiment, the frequency (peak frequency) of the maximum sound absorption rate in the frequency range of 0 to 8000 Hz may be 2000 Hz or less, 1800 Hz or less, 1500 Hz or less, 1200 Hz or less, 1000 Hz or less, 800 Hz or less, or 500 Hz or less.

[0018] According to the porous sound-absorbing material according to this embodiment, it is also possible to obtain excellent acoustic transmission loss in the frequency range of 4000 Hz or less. For example, excellent acoustic transmission loss can be obtained at 1000 Hz, 2000 Hz, or 4000 Hz. According to the porous sound-absorbing material according to this embodiment, an acoustic transmission loss of 10 dB or more (preferably 15 dB or more, more preferably 30 dB or more) can be obtained as the acoustic transmission loss at 1000 Hz, 2000 Hz, or 4000 Hz measured in accordance with ASTM E2611-09.

[0019] Examples of the sound propagation method in the porous body include air propagation in air and solid propagation in a solid. In air propagation, sound can disappear due to viscous loss, heat exchange loss, etc. during propagation. In solid propagation, sound can disappear due to internal loss (energy attenuation) of the solid during propagation. According to the porous sound-absorbing material according to this embodiment, when the porous sound-absorbing material is used in a state where the high-density region is located on the sound source side with respect to the low-density region due to the low-density region and the high-density region having the above-mentioned apparent density, the solid-propagated sound mainly disappears in the high-density region on the incident side, and then the air-propagated sound and the solid-propagated sound preferably disappear in the entire porous sound-absorbing material. Therefore, it is presumed that excellent sound-absorbing characteristics can be obtained. However, the factors for obtaining excellent sound-absorbing characteristics are not limited to the above content.

[0020] According to the porous sound-absorbing material according to this embodiment, since excellent sound-absorbing characteristics can be obtained, even when the sound-absorbing material is thinned or lightened, sufficient sound-absorbing characteristics can be maintained. Therefore, it is possible to achieve both excellent sound-absorbing characteristics and thinning and lightening, and various applications and usage locations of the sound-absorbing material can be ensured. Further, according to the porous sound-absorbing material according to this embodiment, excellent sound-absorbing characteristics can be obtained by using only the porous sound-absorbing material as a single material. According to this embodiment, it is possible to provide an application of a porous body to sound absorption.

[0021] Since the porous sound-absorbing material according to this embodiment is excellent in sound-absorbing characteristics (particularly, sound-absorbing characteristics in the low-frequency range), it can be suitably used as a sound insulation member (sound absorption and insulation material) in vehicles (automobiles, railways, etc.), aircraft, buildings, piping, and the like.

[0022] The shape of the porous sound-absorbing material according to this embodiment is not particularly limited as long as it has the above-described specific low-density region and high-density region, and may be a regular shape or an irregular shape. Examples of the shape of the porous sound-absorbing material include a sheet shape, a columnar shape (cylindrical, polygonal columnar, etc.), a conical shape, a polygonal pyramid shape, and a rod shape.

[0023] As long as it is possible to use the porous sound-absorbing material in a state where the high-density region is located on the sound source side with respect to the low-density region, the positions of the low-density region and the high-density region in the porous sound-absorbing material are not particularly limited. The porous sound-absorbing material according to this embodiment may include a plurality of the above-described specific low-density regions, and may include a plurality of the above-described specific high-density regions.

[0024] The porous sound-absorbing material according to this embodiment is a porous sound-absorbing material including a porous low-density region and a high-density region. "Porous" indicates a form having a large number of holes (voids) in the base material (for example, a form of a foam), and in this specification, each hole is referred to as a "cell". The cell does not necessarily have to be spherical and may be an irregular shape.

[0025] The cells contained in the porous sound-absorbing material may be cells with a closed-cell structure (closed cells) that are arranged independently of each other, or may be cells with an open-cell structure (open cells) in which a plurality of cells communicate with each other. The porous sound-absorbing material may contain at least one selected from the group consisting of closed cells and open cells. In this case, the numerical ratio of closed cells to open cells is not particularly limited. That is, the porous sound-absorbing material (porous body) can have an open-cell structure or a semi-open semi-closed cell structure. The open-cell structure refers to a structure with an open-cell ratio of 100%. The semi-open semi-closed cell structure refers to a structure in which the lower limit of the open-cell ratio exceeds 0% (the open-cell ratio is 10% or more) and the upper limit of the open-cell ratio is less than 100%.

[0026] There is no particular limitation on the method for producing closed cells or open cells. When imparting porosity by foaming, methods such as adjusting the type or addition amount of a foaming agent, a crosslinking agent, etc., adjusting the processing conditions in the foaming process, and mechanically breaking the film (bubble film) between the cells forming the closed cells to connect some or all of the cells to make them continuous can be mentioned. The air permeability and the open-cell structure can be obtained, for example, by subjecting the obtained porous body (for example, a sheet-like foam) to compressive deformation with an equal-speed twin roll or the like to break the bubble film, thereby making the bubbles continuous. Also, by opening innumerable small holes on the surface of the foam (cellular body), the continuity of the bubbles can be promoted. Small holes can also be opened on the surface of the foam (cellular body) by providing innumerable small needles on the surface of the equal-speed twin roll, or by arranging a roll provided with innumerable small needles in front of and / or behind the equal-speed twin roll.

[0027] The porous sound-absorbing material according to the present embodiment may include a region other than the above-described specific low-density region and high-density region, a region arranged between the low-density region and the high-density region (for example, a porous region), a region arranged on the side opposite to the high-density region with respect to the low-density region (for example, a porous region), or a region arranged on the side opposite to the low-density region with respect to the high-density region (for example, a porous region).

[0028] In the porous sound-absorbing material according to the present embodiment, the low-density region may be disposed on one side in the arrangement direction of the low-density region and the high-density region (for example, the thickness direction of the laminate described later), and the high-density region may be disposed on the other side in the arrangement direction of the low-density region and the high-density region. At least one selected from the group consisting of one side and the other side may be a flat surface, a curved surface, a concavo-convex surface, or the like.

[0029] The porous sound-absorbing material according to the present embodiment may be in a mode where the interface between the low-density region and the high-density region is clear, or may be in a mode where the interface between the low-density region and the high-density region is not clear (for example, a mode having a density gradient (density gradient structure)). The low-density region and the high-density region may be in contact with each other and may be fused to each other.

[0030] The porous sound-absorbing material according to the present embodiment may have a laminated structure in which a low-density layer that is a low-density region and a high-density layer that is a high-density region are laminated on each other. The low-density layer and the high-density layer are laminated on each other, and the low-density layer and the high-density layer may be in contact with each other. The porous sound-absorbing material according to the present embodiment may be a laminate having a two-layer structure of a low-density layer and a high-density layer. The porous sound-absorbing material according to the present embodiment may include a layer other than the low-density layer and the high-density layer, and may include a layer disposed between the low-density layer and the high-density layer, a layer disposed on the side opposite to the high-density layer with respect to the low-density layer, or a layer disposed on the side opposite to the low-density layer with respect to the high-density layer.

[0031] When the porous sound-absorbing material according to the present embodiment is a laminate, the thickness of the low-density layer, the thickness of the high-density layer, or the thickness (total thickness) of the porous sound-absorbing material may be in the following range. The thickness can be measured in accordance with ISO 1923 (1981) "Cellular Plastics and Rubbers - Measurement of Linear Dimensions" and may be an average thickness.

[0032] The thickness of the low-density layer may be 0.1 mm or more, 0.3 mm or more, 0.5 mm or more, 0.8 mm or more, 1 mm or more, 1.5 mm or more, 2 mm or more, 2.5 mm or more, more than 2.5 mm, 3 mm or more, 3.5 mm or more, 4 mm or more, 4.5 mm or more, or 5 mm or more from the viewpoint of easily obtaining excellent sound absorption rate. The thickness of the low-density layer may be 5.5 mm or more, 6 mm or more, 6.5 mm or more, 7 mm or more, 7.5 mm or more, 8 mm or more, 8.5 mm or more, or 9 mm or more from the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz. The thickness of the low-density layer may be 30 mm or less, 25 mm or less, 20 mm or less, 18 mm or less, 15 mm or less, 12 mm or less, 10 mm or less, or 9 mm or less from the viewpoints of easily obtaining excellent sound absorption rate and sound transmission loss. The thickness of the low-density layer may be 8.5 mm or less, 8 mm or less, 7.5 mm or less, 7 mm or less, 6.5 mm or less, 6 mm or less, 5.5 mm or less, or 5 mm or less from the viewpoints of easily obtaining excellent sound absorption rate at 1000 Hz and more excellent sound transmission loss. The thickness of the low-density layer may be 4.5 mm or less, 4 mm or less, 3.5 mm or less, 3 mm or less, 2.5 mm or less, less than 2.5 mm, 2 mm or less, 1.5 mm or less, or 1 mm or less from the viewpoint of more easily obtaining more excellent sound transmission loss. From these viewpoints, the thickness of the low-density layer may be 0.1 to 30 mm, 0.1 to 10 mm, 1 to 30 mm, 1 to 10 mm, or 3 to 8 mm.

[0033] The thickness of the high-density layer may be 0.1 mm or more, 0.3 mm or more, 0.5 mm or more, more than 0.5 mm, 0.8 mm or more, or 1 mm or more from the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss. The thickness of the high-density layer may be more than 1 mm, 1.5 mm or more, 2 mm or more, 2.5 mm or more, more than 2.5 mm, 3 mm or more, 3.5 mm or more, 4 mm or more, 4.5 mm or more, or 5 mm or more from the viewpoints of easily obtaining excellent sound absorption rate at 1000 Hz and more easily obtaining more excellent acoustic transmission loss. The thickness of the high-density layer may be 5.5 mm or more, 6 mm or more, 6.5 mm or more, 7 mm or more, 7.5 mm or more, 8 mm or more, 8.5 mm or more, or 9 mm or more from the viewpoint of more easily obtaining more excellent acoustic transmission loss. The thickness of the high-density layer may be 30 mm or less, 25 mm or less, 20 mm or less, 18 mm or less, 15 mm or less, 12 mm or less, 10 mm or less, less than 10 mm, 9 mm or less, 8.5 mm or less, 8 mm or less, 7.5 mm or less, 7 mm or less, 6.5 mm or less, 6 mm or less, 5.5 mm or less, or 5 mm or less from the viewpoint of easily obtaining excellent sound absorption rate. The thickness of the high-density layer may be 4.5 mm or less, 4 mm or less, 3.5 mm or less, 3 mm or less, 2.5 mm or less, less than 2.5 mm, 2 mm or less, 1.5 mm or less, or 1 mm or less from the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz. From these viewpoints, the thickness of the high-density layer may be 0.1 to 30 mm, 0.1 to 10 mm, 1 to 30 mm, 1 to 10 mm, or 3 to 8 mm.

[0034] The ratio A of the thickness of the high-density layer to the thickness of the low-density layer (thickness of high-density layer / thickness of low-density layer) may be in the following range. From the viewpoint of easily obtaining excellent sound absorption rate and sound transmission loss, the ratio A may be 0.01 or more, 0.05 or more, 0.1 or more, or 0.11 or more. From the viewpoint of easily obtaining excellent sound absorption rate at 1000 Hz and further excellent sound transmission loss, the ratio A may be 0.15 or more, 0.2 or more, 0.4 or more, 0.5 or more, 0.8 or more, or 1 or more. From the viewpoint of more easily obtaining excellent sound transmission loss, the ratio A may be more than 1, 1.5 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, or 9 or more. From the viewpoint of easily obtaining excellent sound absorption rate, the ratio A may be 20 or less, 15 or less, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. From the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz, the ratio A may be less than 1, 0.8 or less, 0.5 or less, 0.4 or less, 0.2 or less, 0.15 or less, or 0.11 or less. From these viewpoints, the ratio A may be 0.01 to 20, 0.1 to 20, 0.01 to 10, 0.1 to 10, or 0.5 to 2.

[0035] From the viewpoint of easily obtaining excellent sound absorption rate and sound transmission loss, the thickness of the porous sound-absorbing material may be 1 mm or more, 3 mm or more, 5 mm or more, 8 mm or more, 10 mm or more, 12 mm or more, 15 mm or more, 18 mm or more, or 20 mm or more. From the viewpoints of easily obtaining excellent sound absorption rate and sound transmission loss and reducing the mass of the porous sound-absorbing material, the thickness of the porous sound-absorbing material may be 50 mm or less, 45 mm or less, 40 mm or less, 35 mm or less, 30 mm or less, 25 mm or less, or 20 mm or less. From the viewpoint of further reducing the mass of the porous sound-absorbing material, the thickness of the porous sound-absorbing material may be 15 mm or less, or 10 mm or less. From these viewpoints, the thickness of the porous sound-absorbing material may be 1 to 50 mm, 10 to 50 mm, 1 to 20 mm, 5 to 40 mm, or 5 to 30 mm.

[0036] The apparent density of the low-density region is more than 0 kg / m 3 and less than 100 kg / m 3The following applies. From the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss, the apparent density of the low-density region is 10 kg / m 3 or more, 20 kg / m 3 or more, 25 kg / m 3 or more, or 30 kg / m 3 or more. From the viewpoint of easily obtaining excellent sound absorption rate at 1000 Hz and further excellent acoustic transmission loss, the apparent density of the low-density region is 35 kg / m 3 or more, 40 kg / m 3 or more, 45 kg / m 3 or more, 50 kg / m 3 or more, 50 kg / m 3 exceeding, 55 kg / m 3 or more, 60 kg / m 3 or more, 65 kg / m 3 or more, 70 kg / m 3 or more, 75 kg / m 3 or more, or 80 kg / m 3 or more. From the viewpoint of more easily obtaining excellent acoustic transmission loss, the apparent density of the low-density region is 85 kg / m 3 or more, 90 kg / m 3 or more, or 95 kg / m 3 or more. When the apparent density of the low-density region is 100 kg / m 3 or less, excellent sound absorption rate at 1000 Hz can be obtained. In addition, excellent light weight (for example, light weight for in-vehicle applications) and secondary processability can be obtained, and suitable continuous bubbles can be obtained. From the viewpoint of easily obtaining excellent sound absorption rate, the apparent density of the low-density region is 95 kg / m 3 or less, 90 kg / m 3 or less, 85 kg / m 3 or less, or 80 kg / m 3 or less. From the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz, the apparent density of the low-density region is 75 kg / m 3 or less, 70 kg / m 3 or less, 65 kg / m 3 or less, 60 kg / m 3 or less, 55 kg / m 3 or less, 50 kg / m 3 or less, 50 kg / m 3Less than 45 kg / m 3 40 kg / m or less 3 35 kg / m or less 3 or 30 kg / m or less 3 It may be the following. From these viewpoints, the apparent density in the low-density region is 30 to 100 kg / m 3 30 to 80 kg / m 3 80 to 100 kg / m 3 or 50 to 90 kg / m 3 It may be.

[0037] When the porous sound-absorbing material according to the present embodiment is a laminate, the areal density of the low-density region (low-density layer) may be in the following range. From the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss, the areal density of the low-density region is 0.01 kg / m 2 or more, 0.05 kg / m 2 or more, 0.08 kg / m 2 or more, 0.10 kg / m 2 or more, or 0.15 kg / m 2 or more. From the viewpoint of easily obtaining excellent sound absorption rate at 1000 Hz and further excellent acoustic transmission loss, the areal density of the low-density region is 0.20 kg / m 2 or more, 0.24 kg / m 2 or more, 0.25 kg / m 2 or more, 0.30 kg / m 2 or more, 0.35 kg / m 2 or more, or 0.40 kg / m 2 or more. From the viewpoint of easily obtaining further excellent acoustic transmission loss, the areal density of the low-density region is 0.45 kg / m 2 or more, or 0.50 kg / m 2 or more. The areal density of the low-density region is 0.55 kg / m 2 or more, 0.56 kg / m 2 or more, 0.60 kg / m 2 or more, 0.70 kg / m 2 or more, 0.72 kg / m 2 or more, 0.75 kg / m 2 or more, or 0.80 kg / m 2The above may be satisfied. From the viewpoint of easily obtaining excellent sound absorption rate, the surface density of the low-density region is 1.00 kg / m 2 or less, 1.00 kg / m 2 or less, 0.90 kg / m 2 or less, 0.80 kg / m 2 or less, 0.75 kg / m 2 or less, 0.72 kg / m 2 or less, 0.70 kg / m 2 or less, 0.60 kg / m 2 or less, 0.56 kg / m 2 or less, 0.55 kg / m 2 or less, 0.50 kg / m 2 or less, 0.45 kg / m 2 or less, or 0.40 kg / m 2 or less. From the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz, the surface density of the low-density region is 0.45 kg / m 2 or less, 0.40 kg / m 2 or less, 0.35 kg / m 2 or less, 0.30 kg / m 2 or less, 0.25 kg / m 2 or less, 0.24 kg / m 2 or less, 0.20 kg / m 2 or less, or 0.15 kg / m 2 or less. From these viewpoints, the surface density of the low-density region may be 0.01 - 1.00 kg / m 2 , 0.15 - 0.80 kg / m 2 , 0.15 - 0.40 kg / m 2 , 0.40 - 0.80 kg / m 2 , or 0.20 - 0.50 kg / m 2 .

[0038] The apparent density of the high-density region exceeds 100 kg / m 3 and is 400 kg / m 3 or less. From the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss, the apparent density of the high-density region is 110 kg / m 3 or more, 120 kg / m 3 or more, 130 kg / m 3 or more, or 140 kg / m 3The above may be applicable. From the perspective of easily obtaining excellent sound absorption rate at 1000 Hz and further easily obtaining excellent acoustic transmission loss, the apparent density of the high-density region is 150 kg / m 3 or more, 175 kg / m 3 or more, 200 kg / m 3 or more, 225 kg / m 3 or more, 250 kg / m 3 or more, 275 kg / m 3 or more, or 300 kg / m 3 or more. When the apparent density of the high-density region is 400 kg / m 3 or less, excellent sound absorption rate at 1000 Hz can be obtained. In addition, excellent lightweight property (e.g., lightweight property for in-vehicle applications) and secondary processability can be obtained, and suitable closed cells can be obtained. From the perspective of easily obtaining excellent sound absorption rate, the apparent density of the high-density region is 375 kg / m 3 or less, 350 kg / m 3 or less, 325 kg / m 3 or less, or 300 kg / m 3 or less. From the perspective of easily obtaining excellent sound absorption rate at 2000 Hz, the apparent density of the high-density region is 275 kg / m 3 or less, 250 kg / m 3 or less, 225 kg / m 3 or less, 200 kg / m 3 or less, 175 kg / m 3 or less, 150 kg / m 3 or less, or 140 kg / m 3 or less. From these perspectives, the apparent density of the high-density region may exceed 100 kg / m 3 and be 300 kg / m 3 or less, 140 - 400 kg / m 3 120 - 300 kg / m 3 140 - 300 kg / m 3 or 120 - 200 kg / m 3 and may be applicable.

[0039] When the porous sound-absorbing material according to this embodiment is a laminate, the surface density of the high-density region (high-density layer) may be in the following range. From the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss, the surface density of the high-density region is 0.01 kg / m 2 or more, 0.05 kg / m 2 or more, 0.10 kg / m 2 or more, 0.14 kg / m 2 or more, 0.15 kg / m 2 or more, 0.20 kg / m 2 or more, 0.30 kg / m 2 or more, 0.40 kg / m 2 or more, 0.40 kg / m 2 exceeding, 0.42 kg / m 2 or more, 0.50 kg / m 2 or more, 0.60 kg / m 2 or more, or, 0.70 kg / m 2 or more and may be. From the viewpoint of easily obtaining excellent sound absorption rate at 1000 Hz and the viewpoint of more easily obtaining excellent acoustic transmission loss, the surface density of the high-density region is 0.80 kg / m 2 or more, 0.90 kg / m 2 or more, 0.98 kg / m 2 or more, 1.00 kg / m 2 or more, 1.00 kg / m 2 exceeding, 1.10 kg / m 2 or more, 1.20 kg / m 2 or more, 1.26 kg / m 2 or more, 1.30 kg / m 2 or more, 1.40 kg / m 2 or more, or, 1.50 kg / m 2 or more and may be. From the viewpoint of easily obtaining excellent sound absorption rate, the surface density of the high-density region is 3.00 kg / m 2 or less, 2.75 kg / m 2 or less, 2.50 kg / m 2 or less, 2.25 kg / m 2 or less, 2.00 kg / m 2 or less, 1.75 kg / m 2 or less, 1.60 kg / m 2 or less, or, 1.50 kg / m 2It may be as follows. From the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz, the surface density of the high-density region is 1.40 kg / m 2 Hereinafter, 1.30 kg / m 2 Hereinafter, 1.26 kg / m 2 Hereinafter, 1.20 kg / m 2 Hereinafter, 1.10 kg / m 2 Hereinafter, 1.00 kg / m 2 Hereinafter, 1.00 kg / m 2 Less than, 0.98 kg / m 2 Hereinafter, 0.90 kg / m 2 Hereinafter, 0.80 kg / m 2 Hereinafter, or, 0.70 kg / m 2 It may be as follows. The surface density of the high-density region is 0.60 kg / m 2 Hereinafter, 0.50 kg / m 2 Hereinafter, 0.42 kg / m 2 Hereinafter, 0.40 kg / m 2 Hereinafter, 0.40 kg / m 2 Less than, 0.30 kg / m 2 Hereinafter, 0.20 kg / m 2 Hereinafter, 0.15 kg / m 2 Hereinafter, or, 0.14 kg / m 2 It may be as follows. From these viewpoints, the surface density of the high-density region is 0.01~3.00 kg / m 2 0.01~1.50 kg / m 2 0.10~3.00 kg / m 2 Or, 0.10~1.00 kg / m 2 It may be.

[0040] The ratio B of the apparent density of the high-density region to the apparent density of the low-density region (apparent density of the high-density region / apparent density of the low-density region) may be in the following range. From the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss, the ratio B may be 0.1 or more, 0.5 or more, 1 or more, more than 1, 1.2 or more, 1.4 or more, 1.5 or more, 1.75 or more, 2 or more, 2.25 or more, 2.5 or more, 2.75 or more, 3 or more, 3.25 or more, 3.5 or more, or 3.75 or more. From the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz, the ratio B may be 4 or more, 4.25 or more, or 4.5 or more. From the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss, the ratio B may be 10 or less, 8 or less, 6 or less, or 5 or less. From the viewpoint of easily obtaining excellent sound absorption rate at 1000 Hz and further excellent acoustic transmission loss, the ratio B may be 4.5 or less, 4.25 or less, 4 or less, 3.75 or less, 3.5 or less, 3.25 or less, or 3 or less. From these viewpoints, the ratio B may be 0.1 to 10, 0.1 to 5, 1 to 10, 1 to 5, or 1 to 3.

[0041] The ratio C of the areal density of the high-density region to the areal density of the low-density region (areal density of high-density region / areal density of low-density region) may be in the following range from the viewpoint of easily obtaining a suitable balance between the sound absorption rate and the sound transmission loss. The ratio C may be 0.1 or more, 0.2 or more, 0.5 or more, 0.75 or more, 1 or more, more than 1, 1.2 or more, 1.4 or more, 1.5 or more, 1.75 or more, 2 or more, 2.25 or more, 2.5 or more, 2.75 or more, 3 or more, 3.25 or more, 3.5 or more, 3.75 or more, 4 or more, 4.25 or more, 4.5 or more, 4.75 or more, 5 or more, 6 or more, 8 or more, 10 or more, or 15 or more. The ratio C may be 20 or less, 18 or less, 16 or less, 15 or less, 10 or less, 8 or less, 6 or less, 5 or less, 4.75 or less, 4.5 or less, 4.25 or less, 4 or less, 3.75 or less, 3.5 or less, 3.25 or less, 3 or less, 2.75 or less, 2.5 or less, 2.25 or less, 2 or less, 1.75 or less, 1.5 or less, 1.4 or less, 1.2 or less, 1 or less, less than 1, 0.75 or less, 0.5 or less, or 0.2 or less. From these viewpoints, the ratio C may be 0.1 to 20, 0.1 to 16, or 1 to 4.

[0042] The apparent density of the porous sound-absorbing material according to the present embodiment (the overall apparent density of the porous sound-absorbing material) may be in the following range. The apparent density of the porous sound-absorbing material may be 10 kg / m 3 or more, 30 kg / m 3 or more, 50 kg / m 3 or more, 80 kg / m 3 or more, or 85 kg / m 3 or more. The apparent density of the porous sound-absorbing material may be 90 kg / m 3 or more, 99 kg / m 3 or more, 100 kg / m 3 or more, more than 100 kg / m 3 110 kg / m 3 or more, 120 kg / m 3 or more, 130 kg / m 3 or more, 138 kg / m 3 or more, 140 kg / m 3 or more, 150 kg / m3 180 kg / m or more 3 200 kg / m or more 3 or 230 kg / m or more 3 It may be so. From the viewpoint of easily obtaining an excellent sound absorption rate, the apparent density of the porous sound absorption material is 400 kg / m 3 or less, 350 kg / m 3 or less, 300 kg / m 3 or less, 250 kg / m 3 or less, or 230 kg / m 3 It may be so. From the viewpoint of easily obtaining an excellent sound absorption rate at 2000 Hz, the apparent density of the porous sound absorption material is 200 kg / m 3 or less, 180 kg / m 3 or less, 150 kg / m 3 or less, 140 kg / m 3 or less, 138 kg / m 3 or less, 130 kg / m 3 or less, 120 kg / m 3 or less, 110 kg / m 3 or less, 100 kg / m 3 or less, 100 kg / m 3 less than 99 kg / m 3 or less, 90 kg / m 3 or less, or 85 kg / m 3 It may be so. From these viewpoints, the apparent density of the porous sound absorption material is 10 to 400 kg / m 3 80 to 400 kg / m 3 10 to 250 kg / m 3 80 to 250 kg / m 3 or 100 to 250 kg / m 3 It may be so.

[0043] When the porous sound absorption material according to this embodiment is a laminate, the surface density of the porous sound absorption material (the overall surface density of the porous sound absorption material) may be in the following range. From the viewpoint of easily obtaining an excellent sound absorption rate and acoustic transmission loss, the surface density of the porous sound absorption material is 0.10 kg / m 2 or more, 0.30 kg / m 2 or more, 0.50 kg / m 2 or more, 0.80 kg / m 2 or more, or 0.85 kg / m 2may be as above. From the viewpoint of easily obtaining excellent sound absorption rate at 1000 Hz and further easily obtaining excellent acoustic transmission loss, the surface density of the porous sound-absorbing material is 0.90 kg / m 2 or more, 0.99 kg / m 2 or more, 1.00 kg / m 2 or more, 1.10 kg / m 2 or more, 1.20 kg / m 2 or more, 1.30 kg / m 2 or more, 1.38 kg / m 2 or more, 1.40 kg / m 2 or more, 1.50 kg / m 2 or more, 1.70 kg / m 2 or more, 1.80 kg / m 2 or more, 1.80 kg / m 2 exceeding, 2.00 kg / m 2 or more, 2.20 kg / m 2 or more, or 2.30 kg / m 2 may be as above. From the viewpoint of easily obtaining excellent sound absorption rate, the surface density of the porous sound-absorbing material is 4.00 kg / m 2 or less, 3.50 kg / m 2 or less, 3.00 kg / m 2 or less, 2.50 kg / m 2 or less, or 2.30 kg / m 2 may be as below. From the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz, the surface density of the porous sound-absorbing material is 2.20 kg / m 2 or less, 2.00 kg / m 2 or less, 1.80 kg / m 2 or less, 1.80 kg / m 2 less than, 1.70 kg / m 2 or less, 1.50 kg / m 2 or less, 1.40 kg / m 2 or less, 1.38 kg / m 2 or less, 1.30 kg / m 2 or less, 1.20 kg / m 2 or less, 1.10 kg / m 2 or less, 1.00 kg / m 2 or less, 0.99 kg / m 2 or less, 0.90 kg / m 2 or less, or 0.85 kg / m 2It may be as follows. From these viewpoints, the surface density of the porous sound-absorbing material is 0.10 to 4.00 kg / m 2 , 0.80 to 4.00 kg / m 2 , 0.10 to 2.50 kg / m 2 , 0.80 to 2.50 kg / m 2 , or 1.00 to 2.50 kg / m 2 and may be so.

[0044] The apparent density (mass per unit volume) can be measured in accordance with JIS K 6767 (1999) "Foamed Plastics - Polyethylene - Test Methods". The apparent density can be adjusted by the blending ratio of foaming agents (for example, organic foaming agents or inorganic foaming agents), vulcanization foaming time, foaming temperature, etc. The surface density (mass per unit area) is the product of the apparent density and the thickness.

[0045] From the viewpoint of easily obtaining excellent sound absorption rate, the air permeability in the low-density region is 0.1 cm 3 / cm 2 ·s or more, 0.2 cm 3 / cm 2 ·s or more, 0.3 cm 3 / cm 2 ·s or more, 0.4 cm 3 / cm 2 ·s or more, 0.5 cm 3 / cm 2 ·s or more, 0.6 cm 3 / cm 2 ·s or more, 0.7 cm 3 / cm 2 ·s or more, 0.8 cm 3 / cm 2 ·s or more, 0.9 cm 3 / cm 2 ·s or more, or 1 cm 3 / cm 2 ·s or more and may be so. From the viewpoint of easily obtaining excellent sound absorption rate at 2000 Hz, the air permeability in the low-density region is 1.2 cm 3 / cm 2 ·s or more, 1.5 cm 3 / cm 2 ·s or more, 1.8 cm 3 / cm 2·s or more, or 2 cm 3 / cm 2 ·s or more may be sufficient. From the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss, the air permeability of the low-density region is 5 cm 3 / cm 2 ·s or less, 4.5 cm 3 / cm 2 ·s or less, 4 cm 3 / cm 2 ·s or less, 3.5 cm 3 / cm 2 ·s or less, 3 cm 3 / cm 2 ·s or less, 2.5 cm 3 / cm 2 ·s or less, or 2 cm 3 / cm 2 ·s or less may be sufficient. From the viewpoint of easily obtaining excellent sound absorption rate at 1000 Hz and further excellent acoustic transmission loss, the air permeability of the low-density region is 1.8 cm 3 / cm 2 ·s or less, 1.5 cm 3 / cm 2 ·s or less, 1.2 cm 3 / cm 2 ·s or less, or 1 cm 3 / cm 2 ·s or less may be sufficient. From the viewpoint of more easily obtaining excellent acoustic transmission loss, the air permeability of the low-density region is 0.9 cm 3 / cm 2 ·s or less, 0.8 cm 3 / cm 2 ·s or less, 0.7 cm 3 / cm 2 ·s or less, 0.6 cm 3 / cm 2 ·s or less, 0.5 cm 3 / cm 2 ·s or less, or 0.4 cm 3 / cm 2 ·s or less may be sufficient. From these viewpoints, the air permeability of the low-density region is 0.1 to 5 cm 3 / cm 2 ·s, 0.1 to 2 cm 3 / cm 2 ·s, 0.4 to 5 cm 3 / cm 2 ·s, 0.4 to 2 cm3 / cm 2 ·s, or 0.5 to 1.5 cm 3 / cm 2 ·s may be sufficient.

[0046] From the viewpoint of easily obtaining an excellent sound absorption rate, the air permeability of the high-density region is 0.01 cm 3 / cm 2 ·s or more, 0.03 cm 3 / cm 2 ·s or more, 0.05 cm 3 / cm 2 ·s or more, 0.08 cm 3 / cm 2 ·s or more, or 0.1 cm 3 / cm 2 ·s or more may be sufficient. From the viewpoint of easily obtaining an excellent sound absorption rate at 2000 Hz, the air permeability of the high-density region is 0.15 cm 3 / cm 2 ·s or more, 0.2 cm 3 / cm 2 ·s or more, 0.25 cm 3 / cm 2 ·s or more, or 0.3 cm 3 / cm 2 ·s or more may be sufficient. From the viewpoint of easily obtaining an excellent sound absorption rate and acoustic transmission loss, the air permeability of the high-density region is 2 cm 3 / cm 2 ·s or less, 1.5 cm 3 / cm 2 ·s or less, 1 cm 3 / cm 2 ·s or less, 0.9 cm 3 / cm 2 ·s or less, 0.8 cm 3 / cm 2 ·s or less, 0.7 cm 3 / cm 2 ·s or less, 0.6 cm 3 / cm 2 ·s or less, 0.5 cm 3 / cm 2 ·s or less, 0.4 cm 3 / cm 2 ·s or less, or 0.3 cm 3 / cm 2·s or less may be sufficient. From the viewpoint of easily obtaining an excellent sound absorption rate at 1000 Hz and further easily obtaining an excellent acoustic transmission loss, the air permeability of the high-density region is 0.25 cm 3 / cm 2 ·s or less, 0.2 cm 3 / cm 2 ·s or less, 0.15 cm 3 / cm 2 ·s or less, or 0.1 cm 3 / cm 2 ·s or less may be sufficient. From these viewpoints, the air permeability of the high-density region is 0.01 - 2 cm 3 / cm 2 ·s, 0.1 - 2 cm 3 / cm 2 ·s, 0.01 - 0.3 cm 3 / cm 2 ·s, or 0.1 - 0.3 cm 3 / cm 2 ·s may be sufficient.

[0047] The ratio D (air permeability of high-density region / air permeability of low-density region) of the air permeability of the high-density region to the air permeability of the low-density region may be in the following range from the viewpoint of easily obtaining a suitable balance between the sound absorption rate and the acoustic transmission loss. The ratio D may be 0.01 or more, 0.05 or more, 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, or 0.75 or more. The ratio D may be 2 or less, 1.5 or less, 1 or less, less than 1, 0.8 or less, 0.75 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.25 or less, 0.2 or less, 0.15 or less, or 0.1 or less. From these viewpoints, the ratio D may be 0.01 - 2, 0.1 - 2, 0.01 - 0.75, 0.1 - 0.75, or 0.15 - 0.5.

[0048] The air permeability can be measured by the method described in the examples. The air permeability can be adjusted by the average cell diameter, the maximum cell diameter, the degree of generation of continuous bubbles, the blending ratio of a foaming agent (for example, an organic foaming agent or an inorganic foaming agent), the vulcanization foaming time, the foaming temperature, etc.

[0049] The average cell diameter (the overall average cell diameter of the porous sound-absorbing material; average pore diameter) of the porous sound-absorbing material according to this embodiment may be in the following range. From the viewpoint of easily obtaining an excellent sound absorption rate, the average cell diameter of the porous sound-absorbing material may be 100 μm or more, 150 μm or more, 200 μm or more, 250 μm or more, or 270 μm or more. From the viewpoint of easily obtaining an excellent sound absorption rate at 2000 Hz, the average cell diameter of the porous sound-absorbing material may be 280 μm or more, 290 μm or more, 300 μm or more, 320 μm or more, 350 μm or more, 360 μm or more, 400 μm or more, or 430 μm or more. From the viewpoint of easily obtaining an excellent sound absorption rate and acoustic transmission loss, the average cell diameter of the porous sound-absorbing material may be 600 μm or less, 550 μm or less, 500 μm or less, 450 μm or less, 440 μm or less, or 430 μm or less. From the viewpoints of easily obtaining an excellent sound absorption rate at 1000 Hz and further easily obtaining an excellent acoustic transmission loss, the average cell diameter of the porous sound-absorbing material may be 400 μm or less, 360 μm or less, 350 μm or less, 320 μm or less, 300 μm or less, 290 μm or less, 280 μm or less, or 270 μm or less. From these viewpoints, the average cell diameter of the porous sound-absorbing material may be 100 to 600 μm, 300 to 600 μm, 200 to 450 μm, 250 to 450 μm, 270 to 430 μm, or 270 to 400 μm.

[0050] The porous sound-absorbing material according to this embodiment does not necessarily have bubbles (cells) with a cell diameter of 1000 μm or more, from the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss. The maximum cell diameter (maximum pore diameter) of the porous sound-absorbing material according to this embodiment may be in the following range. From the viewpoint of easily obtaining an excellent sound absorption rate, the maximum cell diameter of the porous sound-absorbing material may be 600 μm or more, 650 μm or more, 700 μm or more, or 750 μm or more. From the viewpoint of easily obtaining an excellent sound absorption rate at 2000 Hz, the maximum cell diameter of the porous sound-absorbing material may be 760 μm or more, 800 μm or more, 850 μm or more, 870 μm or more, 890 μm or more, 900 μm or more, 910 μm or more, 950 μm or more, 960 μm or more, or 970 μm or more. From the viewpoint of easily obtaining excellent sound absorption rate and acoustic transmission loss, the maximum cell diameter of the porous sound-absorbing material may be less than 1000 μm, 980 μm or less, or 970 μm or less. From the viewpoints of easily obtaining an excellent sound absorption rate at 1000 Hz and further easily obtaining excellent acoustic transmission loss, the maximum cell diameter of the porous sound-absorbing material may be 960 μm or less, 950 μm or less, 910 μm or less, 900 μm or less, 890 μm or less, 870 μm or less, 850 μm or less, 800 μm or less, 760 μm or less, or 750 μm or less. From these viewpoints, the maximum cell diameter of the porous sound-absorbing material may be 600 μm or more and less than 1000 μm, 700 to 970 μm, or 750 to 970 μm.

[0051] The average cell diameter and the maximum cell diameter of the porous sound-absorbing material can be measured by image analysis of an image of an arbitrary cross-section of the porous sound-absorbing material. Even when the porous sound-absorbing material contains continuous cells, the average cell diameter and the maximum cell diameter of the porous sound-absorbing material can be measured by the same method. The average cell diameter may be the average value of the cell diameters of 100 bubbles, and the maximum cell diameter may be the maximum value of the cell diameters of 100 bubbles. The average cell diameter and the maximum cell diameter of the porous sound-absorbing material can be adjusted by the blending ratio of a foaming agent (for example, an organic foaming agent or an inorganic foaming agent), the vulcanization foaming time, the foaming temperature, and the like.

[0052] The low-density region and the high-density region in the porous sound-absorbing material according to this embodiment contain ethylene propylene diene rubber (EPDM) as a base material.

[0053] The content of the base material (EPDM) may be in the following range based on the total mass of the porous sound-absorbing material. From the perspective of easily obtaining excellent sound-absorbing characteristics, the content of the base material may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more. From the perspective of easily obtaining excellent sound-absorbing characteristics, the content of the base material may be 90% by mass or less, 85% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less. From these perspectives, the content of the base material may be 10 to 90% by mass.

[0054] The porous sound-absorbing material according to this embodiment may contain a filler. By using the filler, the porous sound-absorbing material can be reinforced. Also, the processability during the production of the porous sound-absorbing material can be improved, etc. As the filler, an inorganic filler (inorganic filler) can be used. The filler may be used alone or in combination of two or more.

[0055] Examples of the constituent materials of the inorganic filler include metal materials, oxides (excluding zinc oxide), nitrides, carbonates, metal hydroxides, carbon-based materials, talc, silicic acid and its salts (for example, aluminum silicate), clay, mica powder, bentonite, etc. Examples of the metal material include a single metal, a mixture of metals, an alloy, etc. The inorganic filler may contain at least one selected from the group consisting of a metal material, an oxide, and a carbonate.

[0056] The inorganic filler may be a metal filler containing a metal material. The metal filler may be a filler made of a metal material. Examples of the metal material include zinc (Zn), iron (Fe), tungsten (W), aluminum (Al), silicon (Si), titanium (Ti), copper (Cu), nickel (Ni), tin (Sn), silver (Ag), gold (Au), alloys containing these metals, and the like. Examples of the alloy include sendust (Fe-Si-Al alloy), iron alloy (excluding sendust, e.g., stainless steel), tungsten alloy, and the like. The inorganic filler may be sendust, zinc alone, or the like.

[0057] Examples of the oxide include silicon oxide (silica), lead monoxide, composite oxides containing these oxides, and the like. Examples of the nitride include boron nitride, aluminum nitride, composite nitrides containing these nitrides, and the like. Examples of the carbonate include calcium carbonate (e.g., heavy calcium carbonate), magnesium carbonate, and the like. Examples of the metal hydroxide include calcium hydroxide, magnesium hydroxide, aluminum hydroxide, and the like. Examples of the carbon-based material include acetylene black, carbon black (such as furnace black, ketjen black, etc.). From the viewpoint of easily obtaining excellent processability, the inorganic filler may contain at least one selected from the group consisting of calcium carbonate and carbon black.

[0058] The content of the filler may be in the following range with respect to 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent strength of the porous sound-absorbing material, the content of the filler may be 10 parts by mass or more, 20 parts by mass or more, 30 parts by mass or more, 50 parts by mass or more, 70 parts by mass or more, 90 parts by mass or more, or 100 parts by mass or more. From the viewpoints of excellent dispersibility, processability in the base material, and appearance of the porous sound-absorbing material, the content of the filler may be 200 parts by mass or less, 180 parts by mass or less, 150 parts by mass or less, 120 parts by mass or less, or 110 parts by mass or less. From these viewpoints, the content of the filler may be 10 to 200 parts by mass.

[0059] The content of the filler may be in the following range based on the total mass of the porous sound-absorbing material. From the viewpoint of easily obtaining excellent sound-absorbing characteristics, the content of the filler may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more. From the viewpoint of easily obtaining excellent sound-absorbing characteristics, the content of the filler may be 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 45% by mass or less, or 40% by mass or less. From these viewpoints, the content of the filler may be 10 to 90% by mass.

[0060] The porous sound-absorbing material according to this embodiment may contain an antioxidant. By using an antioxidant, the heat resistance (the property of suppressing deterioration when maintained at a high temperature) can be improved. Examples of the antioxidant include amine compounds (excluding compounds corresponding to imidazole compounds), imidazole compounds (compounds having an imidazole ring), monophenol compounds (excluding compounds corresponding to amine compounds or imidazole compounds), and the like. The antioxidant may be used alone or in combination of two or more.

[0061] The antioxidant may contain, as an amine compound, an aromatic amine compound (for example, an aromatic secondary amine compound) and may contain a diphenylamine compound. Examples of the amine compound include 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, octylated diphenylamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, and the like.

[0062] The antioxidant may contain, as an imidazole compound, a benzimidazole compound (a compound having a benzimidazole ring). The benzimidazole compound may be a metal salt (for example, a zinc salt). Examples of the imidazole compound include zinc salt of 2-mercaptobenzimidazole and the like.

[0063] At least one selected from the group consisting of a low-density region and a high-density region may contain a diphenylamine compound, and may contain a diphenylamine compound and a benzimidazole compound, from the viewpoint of easily obtaining excellent heat resistance.

[0064] The content of the antioxidant may be in the following range with respect to 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent heat resistance, the content of the antioxidant may be 0.1 part by mass or more, 0.2 part by mass or more, 0.3 part by mass or more, 0.5 part by mass or more, 0.7 part by mass or more, 0.9 part by mass or more, or 1 part by mass or more. From the viewpoint of easily obtaining excellent heat resistance, the content of the antioxidant may be 5 parts by mass or less, 4 parts by mass or less, 3 parts by mass or less, 2 parts by mass or less, 1.8 parts by mass or less, 1.5 parts by mass or less, 1.2 parts by mass or less, or 1.1 parts by mass or less. From these viewpoints, the content of the antioxidant may be 0.1 to 5 parts by mass.

[0065] The content of the antioxidant may be in the following range based on the total mass of the porous sound-absorbing material. From the viewpoint of easily obtaining excellent heat resistance, the content of the antioxidant may be 0.1 mass% or more, 0.15 mass% or more, 0.2 mass% or more, 0.25 mass% or more, 0.3 mass% or more, or 0.35 mass% or more. From the viewpoint of easily obtaining excellent heat resistance, the content of the antioxidant may be 1 mass% or less, 0.8 mass% or less, 0.7 mass% or less, 0.6 mass% or less, 0.5 mass% or less, 0.45 mass% or less, or 0.4 mass% or less. From these viewpoints, the content of the antioxidant may be 0.1 to 1 mass%.

[0066] The porous sound-absorbing material according to this embodiment may contain a softening agent. By using a softening agent, the processability can be improved. Examples of the softening agent include drying oils or animal and vegetable oils (e.g., linseed oil), petroleum-based oils (paraffin-based process oil, naphthenic-based process oil, aromatic-based process oil, etc.), asphalts, low-molecular-weight polymers, organic acid esters (e.g., phthalic acid esters such as di-2-ethylhexyl phthalate (DOP) and dibutyl phthalate (DBP); phosphate esters; higher fatty acid esters; alkyl sulfonic acid esters), thickening agents, and the like. From the viewpoint of easily obtaining excellent foam processability, the softening agent may include petroleum-based oils. The softening agent may be used alone or in combination of two or more.

[0067] The content of the softening agent may be in the following range with respect to 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent foam processability, the content of the softening agent may be 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more. From the viewpoint of easily obtaining excellent foam processability, the content of the softening agent may be 100 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less. From these viewpoints, the content of the softening agent may be 1 to 100 parts by mass.

[0068] The porous sound-absorbing material according to this embodiment may contain a fatty acid. The fatty acid can be used as a processing aid. By using a fatty acid, the processability can be improved. The fatty acid can contain at least one selected from the group consisting of saturated fatty acids and unsaturated fatty acids. The number of carbon atoms of the fatty acid may be 8 to 30, 10 to 20, or 15 to 18. Examples of the fatty acid include stearic acid, palmitic acid, oleic acid, etc. From the viewpoint of easily obtaining excellent foam processability, the fatty acid may include stearic acid. The fatty acid may be used alone or in combination of two or more.

[0069] The content of the fatty acid may be in the following range with respect to 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent foam processing properties, the content of the fatty acid may be 1 part by mass or more, 2 parts by mass or more, or 3 parts by mass or more. From the viewpoint of easily obtaining excellent foam processing properties, the content of the fatty acid may be 10 parts by mass or less, 8 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less. From these viewpoints, the content of the fatty acid may be 1 to 10 parts by mass.

[0070] The porous sound-absorbing material according to the present embodiment may contain any other additive according to the purpose. Examples of the additive include lubricants, plasticizers, nucleating agents, antioxidants, pigments, colorants, fungicides, flame retardants, ultraviolet absorbers, light stabilizers, and the like.

[0071] The porous sound-absorbing material according to the present embodiment may be a foam and can be obtained by foaming a foamable composition containing a foaming agent. The foamable composition according to the present embodiment can contain the components contained in the porous sound-absorbing material and a foaming agent. The expansion ratio (the density ratio before and after foaming. The apparent density after foaming) when the foamable composition is foamed to obtain a foam may be 5 to 30 times.

[0072] The porous sound-absorbing material according to the present embodiment can also be used in a composite integrated form with other materials. For example, the porous sound-absorbing material (such as a sheet-shaped porous sound-absorbing material) can be bonded and integrated with a rubber sheet, a resin sheet, a woven fabric, a non-woven fabric, a gypsum board, a wooden board, a metal plate, etc. for use.

[0073] There is no particular limitation on the manufacturing method of the porous sound-absorbing material according to the present embodiment. In the manufacturing method of the porous sound-absorbing material according to the present embodiment, the porous sound-absorbing material may be obtained by laminating a low-density region and a high-density region, or the porous sound-absorbing material may be obtained by thermally fusing the low-density region and the high-density region.

[0074] An example of the method for manufacturing the porous sound-absorbing material according to the present embodiment may include a foaming step (foamed body manufacturing step) of foaming the first unfoamed body and the second unfoamed body having different compositions while they are laminated on each other to obtain a low-density region and a high-density region. The first unfoamed body and the second unfoamed body may be in contact with each other.

[0075] The first unfoamed body is an unfoamed body for obtaining a low-density region. The second unfoamed body is an unfoamed body for obtaining a high-density region. The first unfoamed body and the second unfoamed body are foaming compositions and contain a base material (ethylene-propylene-diene rubber) and a foaming agent. The compositions of the first unfoamed body and the second unfoamed body (the compositions of the foaming compositions) are different from each other. For example, the types of foaming agents (foaming agents with different decomposition temperatures, etc.), the contents of the foaming agents, etc. are different from each other. By making the amount of gas generated and the generation rate during foaming in the unfoamed body different, a low-density region and a high-density region can be obtained. The first unfoamed body and the second unfoamed body may contain a filler, an antioxidant, a processing aid, a softening agent, a crosslinking agent, a crosslinking accelerator, a foaming aid, etc. as necessary.

[0076] In the foaming step, the foaming composition can be foamed by heating the foaming composition. In the foaming step, a foaming method of foaming the foaming composition in a closed mold, a foaming method of freely expanding and foaming the foaming composition, etc. can be performed. The foaming composition to be foamed may be, for example, a sheet body obtained by forming the foaming composition into a sheet shape. As the foaming method of foaming the foaming composition in a closed mold, a method of placing the foaming composition in a metal mold and then foaming it by arranging the entire metal mold between the hot plates of a hot press can be used. Also, as the foaming method of freely expanding and foaming the foaming composition, a method of placing the foaming composition as it is in an oven, heating it, and foaming it can be used.

[0077] The expansion ratio, apparent density, air permeability, average cell diameter, maximum cell diameter, etc. of the foam can be adjusted by the blending ratio of various components when manufacturing the foam; conditions such as kneading and foaming. However, even when the same manufacturing method or apparatus is used, the foaming phenomenon tends to be easily influenced by delicate factors (for example, differences in the elapsed time from one process to the next), and also tends to be easily influenced by the size of the apparatus etc. even though the operating principle is the same. Therefore, it may be difficult to obtain foams having exactly the same attributes. In such a case, the blending composition or processing conditions can be adjusted by an operator having ordinary knowledge in the technical field.

[0078] The method for manufacturing the porous sound-absorbing material according to the present embodiment may include a composition preparation step of obtaining a foamable composition by mixing a base material (ethylene-propylene-diene rubber) and a foaming agent before the foaming step.

[0079] The composition preparation step may have, in this order, a kneading step of kneading the base material to obtain a kneaded product (kneaded base material), a first kneading step of mixing the kneaded product with additives other than the foaming agent (filler, antioxidant, softening agent, processing aid, etc.) to obtain a first kneaded product, and a second kneading step of mixing the first kneaded product and the foaming agent to obtain a foamable composition (second kneaded product). Depending on the type or physical properties of the base material, the kneading step can be omitted. In the second kneading step, in addition to the foaming agent, a foaming aid, a crosslinking agent, a crosslinking accelerator, a crosslinking retarder, etc. may be added.

[0080] The foaming agents are classified into solid compounds that decompose to generate gas, liquids that vaporize when heated, inert gases that can be dissolved in the base material under pressure, etc., and any of these can be used. Examples of the foaming agent include organic foaming agents and inorganic foaming agents. The foaming agent may be used alone or in combination of two or more.

[0081] Examples of the organic foaming agent include azo compounds, N-nitroso compounds, hydrazide compounds, semicarbazide compounds, fluorinated alkanes, triazole compounds, etc.

[0082] Examples of azo compounds include azodicarbonamide (ADCA), barium azodicarboxylate, azobisisobutyronitrile (AIBN), azocyclohexylnitrile, azodiaminobenzene, etc. Examples of N-nitroso compounds include N,N'-dinitrosopentamethylenetetramine (DTP), N,N'-dimethyl-N,N'-dinitrosoterephthalamide, trinitrosotrimethyltriamine, etc. Examples of hydrazide compounds include 4,4'-oxybis(benzenesulfonylhydrazide) (OBSH), paratoluenesulfonylhydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, 2,4-toluenedisulfonylhydrazide, p,p-bis(benzenesulfonylhydrazide) ether, benzene-1,3-disulfonylhydrazide, allylbis(sulfonylhydrazide), etc. Examples of semicarbazide compounds include p-tolylenesulfonyl semicarbazide, 4,4'-oxybis(benzenesulfonyl semicarbazide), etc. Examples of fluorinated alkanes include trichloromonofluoromethane, dichloromonofluoromethane, etc. Examples of triazole compounds include 5-morpholyl-1,2,3,4-thiatriazole, etc.

[0083] Examples of inorganic blowing agents include hydrogen carbonates such as sodium hydrogen carbonate and ammonium hydrogen carbonate; carbonates such as sodium carbonate and ammonium carbonate; nitrites such as sodium nitrite and ammonium nitrite; boron hydride salts such as sodium borohydride; azides, etc.

[0084] From the viewpoint of easily obtaining excellent foamability, the blowing agent may contain an organic blowing agent, may contain at least one selected from the group consisting of azo compounds and N-nitroso compounds, and may contain at least one selected from the group consisting of azodicarbonamide (ADCA) and N,N'-dinitrosopentamethylenetetramine (DTP).

[0085] The amount of the foaming agent used may be in the following range with respect to 100 parts by mass of the base material. From the viewpoint of easily obtaining excellent foamability, the amount of the foaming agent used may be 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 5 parts by mass or more, 8 parts by mass or more, 10 parts by mass or more, 12 parts by mass or more, 15 parts by mass or more, or 17 parts by mass or more. From the viewpoint of easily suppressing a decrease in the rigidity of the porous sound-absorbing material due to excessive foaming, the amount of the foaming agent used may be 30 parts by mass or less, 25 parts by mass or less, 20 parts by mass or less, or 17 parts by mass or less. From these viewpoints, the amount of the foaming agent used may be 1 to 30 parts by mass.

[0086] Examples of the foaming aid include urea-based compounds (such as urea), salicylic acid-based compounds, benzoic acid-based compounds, and the like.

[0087] Examples of the crosslinking agent include sulfur, sulfur compounds (such as polysulfide, 4,4'-dithiomorpholine, etc.), selenium, organic peroxides (such as cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, acetylacetone peroxide, etc.), polyamines, oximes (such as p-quinonedioxime, p,p'-dibenzoylquinonedioxime, etc.), nitroso compounds (such as p-dinitrosobenzene), ammonium salts (such as ammonium benzoate), metal oxides (such as magnesium oxide), and the like. The metal oxide may also have the function of a filler.

[0088] The content of the crosslinking agent may be in the following range with respect to 100 parts by mass of the base material. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking agent may be 0.1 part by mass or more, 0.5 part by mass or more, 1 part by mass or more, 1.5 part by mass or more, or 2 parts by mass or more. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking agent may be 10 parts by mass or less, 8 parts by mass or less, 5 parts by mass or less, or 2 parts by mass or less. From these viewpoints, the content of the crosslinking agent may be 1 to 10 parts by mass.

[0089] Examples of the crosslinking accelerator include thiazoles (such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide), dithiocarbamic acids (for example, dithiocarbamates such as sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, zinc dimethyldithiocarbamate, and zinc diethyldithiocarbamate), guanidines (such as diphenylguanidine and di-o-tolylguanidine), sulfenamides (such as benzothiazyl-2-diethylsulfenamide and N-cyclohexyl-2-benzothiazylsulfenamide), thiurams (such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide), xanthic acids (such as sodium isopropylxanthate and zinc isopropylxanthate), aldehyde ammonias (such as acetaldehyde ammonia and hexamethylenetetramine), aldehyde amines (such as n-butylaldehyde aniline and butylaldehyde monobutylamine), thioureas (such as diethylthiourea and trimethylthiourea), zinc oxide, and the like.

[0090] The content of the crosslinking accelerator may be in the following range with respect to 100 parts by mass of the base material. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking accelerator may be 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, or 8 parts by mass or more. From the viewpoint of balancing foaming and crosslinking, the content of the crosslinking accelerator may be 20 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, or 8 parts by mass or less. From these viewpoints, the content of the crosslinking accelerator may be 1 to 20 parts by mass.

[0091] Examples of the crosslinking retarder include organic acids (such as phthalic anhydride, benzoic acid, and salicylic acid), amines (such as N-nitroso-diphenylamine and N-nitroso-phenyl-β-naphthylamine), and the like.

[0092] The manufacturing method of the porous sound-absorbing material according to this embodiment may include a compression step (compression continuous connection step) of mechanically compressing the foam after the foaming step. In the compression step, by mechanically compressing the foam, a part or all of the independent cells contained in the foam can be made into continuous cells. In the compression step, the foam is compressed to mechanically break a part of the walls of the cells (for example, independent cells) contained in the foam, and the foam can be made continuous so as to increase the number of continuous cells in which a plurality of cells communicate with each other. In the compression step, it can be carried out by compressing the foam using a press machine, two-rolls, etc. The pressure applied to the foam or the number of presses can be adjusted according to the target foam.

[0093] The process from the above-mentioned kneading step to the compression step can be carried out separately for each step, or some or all of the steps may be carried out continuously. When some or all of the steps are carried out continuously, a continuous device capable of carrying out these steps continuously can be used.

[0094] The sound-absorbing method according to this embodiment includes a sound-absorbing step of absorbing sound using the porous sound-absorbing material according to this embodiment. In the sound-absorbing method according to this embodiment, it is possible to absorb sound by arranging the porous sound-absorbing material in the sound transmission path of the sound to be absorbed, and the high-density region of the porous sound-absorbing material may be located on the sound source side with respect to the low-density region.

[0095] In the sound-absorbing step, the sound to be absorbed can be absorbed, and the sound in a specific frequency range can be absorbed. The frequency range of the sound to be absorbed may be 8000 Hz or less, 4000 Hz or less, 2000 Hz or less, or 1000 Hz or less. In the sound-absorbing step, for example, the sound of 1000 Hz or less can be absorbed.

Examples

[0096] Hereinafter, the content of the present invention will be described in more detail using examples and comparative examples, but the present invention is not limited to the following examples.

[0097] <Materials used> (Base material) Ethylene Propylene Diene Monomer Rubber (EPDM): Manufactured by Mitsui Chemicals, Inc., product name "EMB-EPT4021" (Filler) Calcium carbonate: Manufactured by Maruo Calcium Co., Ltd., product name "Heavy calcium carbonate", crushed Carbon black: Manufactured by Asahi Carbon Co., Ltd., product name "#50" (Antioxidant) Antioxidant A: Aromatic secondary amine compound (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine), manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C" Antioxidant B: Aromatic secondary amine compound (4,4'-bis(α,α-dimethylbenzyl)diphenylamine), manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac CD" Antioxidant C: Benzimidazole compound (zinc salt of 2-mercaptobenzimidazole), manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac MBZ" (Processing aid) Stearic acid: Manufactured by NOF Corporation, product name "Powdered stearic acid sakura" (Softening agent) Paraffinic process oil: Manufactured by Nippon Sun Oil Co., Ltd., product name "SUNPAR150" (Vulcanizing agent) Sulfur: Manufactured by Higashiichi Co., Ltd., product name "Alpha gran S-50EN", sulfur masterbatch (Vulcanization accelerator) Dithiocarbamate: Manufactured by Ouchi Shinko Co., Ltd., product name "Nocceler EZ", zinc diethyldithiocarbamate Thiurams: Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocceler TT", tetramethylthiuram disulfide Zinc oxide powder: Manufactured by Sakai Chemical Industry Co., Ltd., product name "Zinc oxide type 2" (Blowing agent) Azodicarbonamide: Manufactured by Sankyo Kasei Co., Ltd., product name "Celmic C-1" (Blowing aid) Urea: Manufactured by Eimei Kasei Kogyo Co., Ltd., product name "Celpaste 101"

[0098] <Manufacture of Porous Sound Absorbing Material (Foam)> (Example 1) Using a mixing roll (7 inches, rotation speed: 25 rpm) with a roll temperature of 40°C, 100 parts by mass of EPDM (base material) was kneaded for 5 minutes. Then, to this EPDM, 40 parts by mass of calcium carbonate, 10 parts by mass of carbon black, 1 part by mass of antioxidant A, 3 parts by mass of processing aid, and 30 parts by mass of softening agent were added and kneaded for 15 minutes. Subsequently, heat treatment was performed for 3 minutes by raising the roll temperature to 70°C, and then the roll temperature was lowered to 40°C. Then, 2 parts by mass of crosslinking agent, 2 parts by mass of dithiocarbamate (crosslinking accelerator), 1 part by mass of thiurams (crosslinking accelerator), 5 parts by mass of zinc oxide powder (crosslinking accelerator), 17 parts by mass of foaming agent, and 1.5 parts by mass of foaming aid were added and kneaded for 10 minutes to obtain a pre-foamed foamable composition A for the low-density layer.

[0099] Using a mixing roll (7 inches, rotation speed: 25 rpm) with a roll temperature of 40°C, 100 parts by mass of EPDM (base material) was kneaded for 5 minutes. Then, to this EPDM, 40 parts by mass of calcium carbonate, 10 parts by mass of carbon black, 1 part by mass of antioxidant A, 3 parts by mass of processing aid, and 30 parts by mass of softening agent were added and kneaded for 15 minutes. Subsequently, heat treatment was performed for 3 minutes by raising the roll temperature to 70°C, and then the roll temperature was lowered to 40°C. Then, 2 parts by mass of crosslinking agent, 2 parts by mass of dithiocarbamate (crosslinking accelerator), 1 part by mass of thiurams (crosslinking accelerator), 5 parts by mass of zinc oxide powder (crosslinking accelerator), 8 parts by mass of foaming agent, and 1.5 parts by mass of foaming aid were added and kneaded for 10 minutes to obtain a pre-foamed foamable composition B for the high-density layer.

[0100] Subsequently, using a mixing roll (7 inches, rotation speed: 25 rpm) with a roll temperature of 40°C, each of the above foamable compositions was formed into a sheet with a thickness of 5 mm to obtain a sheet A for the low-density layer and a sheet B for the high-density layer, each with a size of 10 cm square. After stacking these sheets one by one on top of each other, they were placed in the center of the recess of a mold having a recess (recess shape: 12 mm (height) × 10 cm × 10 cm). Using a press machine at 110°C, 45 kgf / cm 2、A primary foam was obtained by performing primary foaming under the conditions of 40 minutes.

[0101] After taking out the primary foam from the mold, secondary foaming was carried out by heating it in a hot air circulation oven at 160 °C for 20 minutes to obtain a secondary foam. The secondary foam was passed through between two rolls with a roll interval set at 20 mm three times to make the bubbles continuous. By performing slicing so as to include the boundary portion between the low-density layer and the high-density layer, a sheet-like porous sound-absorbing material (laminated body. Total thickness: 10 mm) having a low-density layer (thickness: 5 mm) and a high-density layer (thickness: 5 mm) was obtained.

[0102] (Example 2) A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that in the slicing process, the thickness of the low-density layer was adjusted to 7 mm and the thickness of the high-density layer was adjusted to 3 mm.

[0103] (Example 3) A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that in the slicing process, the thickness of the low-density layer was adjusted to 9 mm and the thickness of the high-density layer was adjusted to 1 mm.

[0104] (Example 4) A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that in the slicing process, the thickness of the low-density layer was adjusted to 3 mm and the thickness of the high-density layer was adjusted to 7 mm.

[0105] (Example 5) A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that in the slicing process, the thickness of the low-density layer was adjusted to 1 mm and the thickness of the high-density layer was adjusted to 9 mm.

[0106] (Example 6) A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that the addition amount of the foaming agent was changed to 4 parts by mass when preparing the foaming composition B.

[0107] (Example 7) In the preparation of the foaming composition A, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that the addition amount of the foaming agent was changed to 12 parts by mass.

[0108] (Example 8) In the preparation of the foaming composition A, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that the addition amount of the foaming agent was changed to 20 parts by mass and the addition amount of the dithiocarbamate (crosslinking accelerator) was changed to 1.5 parts by mass.

[0109] (Example 9) In the preparation of the foaming composition A, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that the addition amount of the foaming agent was changed to 12 parts by mass. In the preparation of the foaming composition B, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that the addition amount of the foaming agent was changed to 4 parts by mass.

[0110] (Example 10) A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that the thicknesses of Sheet A for the low-density layer and Sheet B for the high-density layer were changed to 10 mm, a mold having a concave portion (concave portion shape: 24 mm (height) × 10 cm × 10 cm) was used as the mold with a concave portion, and the thickness of the low-density layer was adjusted to 10 mm and the thickness of the high-density layer was adjusted to 10 mm in the slicing process.

[0111] (Example 11) In the preparation of the foaming composition A and the foaming composition B, a sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that 2 parts by mass of antioxidant B and 1 part by mass of antioxidant C were used instead of 1 part by mass of antioxidant A.

[0112] (Comparative Example 1) A sheet-like porous sound-absorbing material was obtained in the same manner as in Example 1, except that Sheet A was not used, Sheet B was formed to a thickness of 10 mm, and the thickness was adjusted to 10 mm in the slicing process.

[0113] (Comparative Example 2) Without using Sheet A, the amount of blowing agent added was changed to 4 parts by mass in the preparation of the foaming composition B, and the same procedure as in Example 1 was carried out except that Sheet B was molded to a thickness of 10 mm and the thickness was adjusted to 10 mm in the slicing process, to obtain a sheet-like porous sound-absorbing material.

[0114] (Comparative Example 3) Without using Sheet B, the amount of blowing agent added was changed to 20 parts by mass in the preparation of the foaming composition A, and the amount of dithiocarbamate (crosslinking accelerator) added was changed to 1.5 parts by mass. The same procedure as in Example 1 was carried out except that Sheet A was molded to a thickness of 10 mm and the thickness was adjusted to 10 mm in the slicing process, to obtain a sheet-like porous sound-absorbing material.

[0115] (Comparative Example 4) Without using Sheet B, the amount of blowing agent added was changed to 12 parts by mass in the preparation of the foaming composition A. The same procedure as in Example 1 was carried out except that Sheet A was molded to a thickness of 10 mm and the thickness was adjusted to 10 mm in the slicing process, to obtain a sheet-like porous sound-absorbing material.

[0116] (Comparative Example 5) The same procedure as in Example 1 was carried out except that the amount of blowing agent added was changed to 20 parts by mass in the preparation of the foaming composition A and the amount of dithiocarbamate (crosslinking accelerator) added was changed to 1.5 parts by mass, and the amount of blowing agent added was changed to 3 parts by mass in the preparation of the foaming composition B and the amount of thiurams (crosslinking accelerator) added was changed to 2 parts by mass, to obtain a sheet-like porous sound-absorbing material.

[0117] (Comparative Example 6) The same procedure as in Example 1 was carried out except that the amount of blowing agent added was changed to 15 parts by mass in the preparation of the foaming composition A and the amount of blowing agent added was changed to 13 parts by mass in the preparation of the foaming composition B, to obtain a sheet-like porous sound-absorbing material.

[0118] (Comparative Example 7) When preparing the foaming composition A, the addition amount of the foaming agent was changed to 7 parts by mass and the addition amount of thiurams (crosslinking accelerators) was changed to 1.5 parts by mass. When preparing the foaming composition B, the addition amount of the foaming agent was changed to 3 parts by mass and the addition amount of thiurams (crosslinking accelerators) was changed to 2 parts by mass. Otherwise, it was carried out in the same manner as in Example 1 to obtain a sheet-like porous sound-absorbing material.

[0119] <Physical Property Measurement> According to the procedure shown below, the density and thickness of the low-density layer, high-density layer, and porous sound-absorbing material (laminate of the low-density layer and high-density layer) were measured, the air permeability of the low-density layer and high-density layer was measured, and the cell diameter of the porous sound-absorbing material was measured. The results are shown in Table 1 and Table 2.

[0120] (Density) The apparent density of the low-density layer, high-density layer, and porous sound-absorbing material was measured according to JIS K 6767 (1999) "Foamed Plastics - Polyethylene - Test Methods". Specifically, after cutting out a plate-shaped test piece with a length of 2 cm and a width of 2 cm from the measurement object, the mass of the test piece was measured, and the mass per unit volume (apparent density) was calculated. Also, the product of the above-mentioned apparent density and thickness was calculated as the areal density.

[0121] (Thickness) According to ISO 1923 (1981) "Foamed Plastics and Rubbers - Measurement of Linear Dimensions", the thicknesses of the low-density layer, high-density layer, and porous sound-absorbing material were measured. Specifically, the thickness was measured using a dial gauge with a measurement area of about 10 cm 2 and.

[0122] (Air Permeability) Using a ventilation tester (product name: KES-F8-AP1, manufactured by Kato Tech Co., Ltd.), the ventilation resistance R (Pa·s / m) of the low-density layer and the high-density layer was measured by the steady-flow differential pressure measurement method as a measure representing the degree of air permeability. Specifically, after adjusting the thickness of the low-density layer and the high-density layer to 5 mm, the measurement object was placed in the center of the ventilation path so as to block the inside of the cylindrical ventilation path. When the thickness of the measurement object exceeded 5 mm, the thickness was adjusted by slicing, and when the thickness of the measurement object was less than 5 mm, a plurality of layers were laminated to adjust the thickness. Then, with a constant ventilation volume V, the pressure difference between the pressure P1 on one end side in the ventilation path and the pressure P2 on the other end side in the ventilation path was measured. The ventilation resistance R was obtained from the following formula. R = (P1 - P2) / V [P1 and P2 represent pressure (Pa), and V represents the ventilation volume per unit area (m 3 / m 2 ·s). The ventilation resistance R (Pa·s / m) has a relationship of C = 1 / R with respect to the air permeability C (m / Pa·s).]

[0123] (Cell diameter) The average cell diameter (average value of cell diameters) and the maximum cell diameter (maximum value of cell diameters) of the porous sound-absorbing material were measured. Specifically, using a desktop scanning electron microscope (JCM6000Plus NeoScope, manufactured by JEOL Ltd.), an image of the bubble part of the porous sound-absorbing material was captured, and the cell diameter (μm) was calculated by performing image analysis (conversion to equivalent circle diameter) on the image based on image analysis software (Mac-View, manufactured by Mount Tech Co., Ltd.). After obtaining the cell diameters of 100 bubble parts of the porous sound-absorbing material, the arithmetic mean value of the 100 cell diameters was obtained as the average cell diameter (μm). Also, the maximum value among the 100 cell diameters was obtained as the maximum cell diameter.

[0124] <Evaluation> The heat resistance temperature, sound absorption rate, and acoustic transmission loss of the porous sound-absorbing material were evaluated according to the procedure shown below. The results are shown in Table 1 and Table 2.

[0125] (Heat resistance temperature) After obtaining three 10 cm square test pieces using a porous sound-absorbing material, the test pieces were stored at 80 °C, 110 °C, or 150 °C for 200 hours each. Subsequently, after leaving the test pieces standing at 24 °C and 50% RH for 24 hours or more, the maximum temperature at which the appearance change and sound absorption rate of the test pieces did not change before and after heating was obtained as the heat resistance temperature. As the appearance change of the test pieces, it was observed that there was no melting of the foam, no size change before and after the test, no defects, and no discoloration.

[0126] (Sound absorption rate) Using an acoustic tube (manufactured by Ono Sokki Co., Ltd., SR-4100), the sound absorption rate was measured in accordance with JIS A 1405-2. Specifically, a porous sound-absorbing material was punched out with a punching blade of φ29 mm to produce a cylindrical test piece. Using this test piece, the sound absorption rate in the range of frequencies from 0 Hz to 8000 Hz was measured. When producing a test piece using a porous sound-absorbing material having a low-density layer and a high-density layer, the sound absorption rate was measured in a state where the high-density layer of the test piece was located on the sound source side with respect to the low-density layer. The sound absorption rate at 1000 Hz and 2000 Hz was obtained, and the frequency at which the sound absorption rate was maximum within the measurement range was obtained as the "peak frequency". When the sound absorption rate at 1000 Hz was 0.40 or more, it was judged to be good.

[0127] (Sound transmission loss) Using an acoustic tube system manufactured by Bruel & Kjaer (PULSE analyzer; hardware: Type3160-A-042, 3050-A-060; software: PULSE Labshop, MS1023), the sound transmission loss was measured in accordance with ASTM E2611-09. Specifically, a porous sound-absorbing material was punched out with a punching blade of φ29 mm to produce a cylindrical test piece. When producing a test piece using a porous sound-absorbing material having a low-density layer and a high-density layer, the sound absorption rate was measured in a state where the high-density layer of the test piece was located on the sound source side with respect to the low-density layer. Using this test piece, the sound transmission loss in the range of frequencies from 0 Hz to 10000 Hz was measured, and the sound transmission loss (unit: dB) at 1000 Hz, 2000 Hz, and 4000 Hz was obtained.

[0128]

Table 1

[0129]

Table 2

Claims

1. comprising a low-density region and a high-density region, wherein the low-density region and the high-density region contain ethylene propylene diene rubber, the apparent density of the low-density region is 75 to 100 kg / m3, the apparent density of the high-density region is greater than 100 kg / m ３ and less than or equal to 400 kg / m ３ The porous sound-absorbing material described above.

2. The porous sound-absorbing material according to claim 1, wherein the average cell diameter of the porous sound-absorbing material is 250 to 450 μm.

3. The porous sound-absorbing material according to claim 1 or 2, which does not have bubbles with a cell diameter of 1000 μm or more.

4. The surface density of the porous sound-absorbing material is 1.70 kg / m ２ The porous sound-absorbing material according to any one of claims 1 to 3, which is less than or equal to the following.

5. The porous sound-absorbing material according to any one of claims 1 to 4, wherein at least one selected from the group consisting of the low-density region and the high-density region further contains a diphenylamine compound.

6. The porous sound-absorbing material according to any one of claims 1 to 4, wherein at least one selected from the group consisting of the low-density region and the high-density region further contains a diphenylamine compound and a benzimidazole compound.

7. The porous sound-absorbing material according to any one of claims 1 to 4, which is a laminate having a two-layer structure of a low-density layer that is the low-density region and a high-density layer that is the high-density region.

8. comprising a sound-absorbing step of absorbing sound using the porous sound-absorbing material according to any one of claims 1 to 7, In the sound-absorbing step, a sound-absorbing method in which the high-density region of the porous sound-absorbing material is located on the sound source side with respect to the low-density region.

9. The sound absorption method according to claim 8, wherein sound of 1000 Hz or less is absorbed in the sound absorption step.

10. A method for manufacturing a porous sound-absorbing material according to any one of claims 1 to 7, comprising a step of obtaining the low-density region and the high-density region by foaming the first unfoamed body and the second unfoamed body in a state where the first unfoamed body and the second unfoamed body having different compositions are laminated on each other, A method for manufacturing a porous sound-absorbing material, wherein the first unfoamed body and the second unfoamed body contain ethylene propylene diene rubber and a foaming agent.

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