Soundproofing materials

Abstract

The present invention provides a soundproofing member having sound absorption and sound insulation properties, comprising a low-density foam layer and a high-density foam layer that maintains a framework, and a method for manufacturing the same. [Solution] The soundproofing member 10 comprises a low-density foam layer 30 and a high-density foam layer 40 which is arranged on one surface 32 in the thickness direction of the low-density foam layer 30 and has a higher density than the low-density foam layer 30. The high-density foam layer 40 maintains its framework and has breathability throughout the thickness direction of the low-density foam layer 30 and the high-density foam layer 40.

Description

[Technical Field]

[0001] This disclosure relates to a soundproofing member having sound absorption and sound insulation properties. [Background technology]

[0002] Patent Document 1 describes materials with a thickness of 1 to 100 mm and a density of 0.01 to 0.2 g / cm³. 3 It has a lightweight sound-absorbing layer and a basis weight of 600g / m². 2 The following soundproofing material is disclosed, in which a non-permeable resonant layer is bonded to the sound-absorbing layer via an adhesive layer. The sound-absorbing layer is formed as a multilayer body of a high-density sound-absorbing layer and a low-density sound-absorbing layer. The resonant layer absorbs sound by membrane resonance, and is preferably a film or 0.02~0.1 g / cm³ 3 Preferably, 0.03 to 0.06 g / cm³ 3 It is an olefin-based foam.

[0003] Patent Document 2 discloses a sound-absorbing material having a breathable thin film on one side of a flexible polyurethane foam board. The breathable thin film is formed by the thermal melting of the flexible polyurethane foam board. Specifically, a 2 mm thick polyester polyurethane foam is placed on one side of a polyether polyurethane foam, and the polyester foam is brought into contact with one roll heated to 380°C and compressed to weld the thermally melted thin film of the polyester foam. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-227747 [Patent Document 2] Japanese Patent Application Publication No. 56-142054 [Overview of the project] [Problems that the invention aims to solve]

[0005] This disclosure provides a novel soundproofing material having sound absorption and sound insulation properties.

Means for Solving the Problem

[0006] A soundproof member according to one aspect of the present disclosure includes a low-density foam layer and a high-density foam layer disposed on one surface in the thickness direction of the low-density foam layer and having a higher density than the low-density foam layer. The high-density foam layer retains its skeleton and has air permeability throughout the thickness direction of the low-density foam layer and the high-density foam layer.

Effect of the Invention

[0007] According to the present disclosure, a soundproof member having a low-density foam layer and a high-density foam layer retaining its skeleton and having sound absorption and sound insulation properties can be provided.

Brief Description of the Drawings

[0008] [Figure 1] Cross-sectional view of a soundproof member according to an embodiment of the present disclosure. [Figure 2] Enlarged cross-sectional view of a soundproof member according to an embodiment of the present disclosure. [Figure 3] Schematic diagram of a manufacturing method of a soundproof member according to an embodiment of the present disclosure. [Figure 4] Enlarged cross-sectional photograph of a soundproof member according to an example of the present disclosure. [Figure 5] Enlarged cross-sectional photograph of a high-density foam layer according to an example of the present disclosure. [Figure 6] Observation schematic diagram of cell size in the thickness direction T of the high-density foam layer shown in FIG. 5. [Figure 7] Photograph of the bottom surface of the low-density foam layer when the soundproof member according to an example of the present disclosure is viewed from the first surface side. [Figure 8] Photograph of the upper surface of the high-density foam layer when the soundproof member according to an example of the present disclosure is viewed from the second surface side. [Figure 9] Test data of transmission loss in examples and comparative examples of the present disclosure. [Figure 10] Test data of insertion loss in examples and comparative examples of the present disclosure. [Figure 11] Test data of normal incidence sound absorption rate in examples and comparative examples of the present disclosure. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings. Unless otherwise specified, numerical ranges indicated using "~" include both the lower and upper limits. For example, the notation "1~5" includes both the lower limit "1" and the upper limit "5".

[0010] Figure 1 is a cross-sectional view of the soundproofing member 10 according to the present disclosure when it is placed on a horizontal plane, and Figure 2 is an enlarged cross-sectional view of the soundproofing member 10 shown in Figure 1. In Figures 1 and 2, arrow H indicates the horizontal direction H of the soundproofing member 10, arrow T indicates the thickness direction T of the soundproofing member 10 perpendicular to the horizontal direction H, and arrow W indicates the width direction W of the soundproofing member 10 perpendicular to the horizontal direction H and the thickness direction T, respectively.

[0011] As shown in Figures 1 and 2, the soundproofing member 10 has a first surface 11 on the horizontal side (bottom side) and a second surface 12 on the opposite side of the first surface 11 (top side). This soundproofing member 10 comprises a low-density foam layer 30 and a high-density foam layer 40 which has a higher density than the low-density foam layer 30.

[0012] In this soundproofing member 10, the low-density foam layer 30 is positioned on the lower side, and the high-density foam layer 40 is positioned on the upper side. The first lower surface 11 of the soundproofing member 10 is also the bottom surface 31 of the low-density foam layer 30, and the second upper surface 12 of the soundproofing member 10 is also the top surface 42 of the high-density foam layer 40.

[0013] Thus, in the soundproofing member 10, a low-density foam layer 30 is arranged on the first surface 11 side (horizontal surface side), a high-density foam layer 40 is arranged on the second surface 12 side, and the high-density foam layer 40 is placed on the upper surface 32 of the low-density foam layer 30.

[0014] An interface 13 is formed at the boundary between the low-density foam layer 30 and the high-density foam layer 40. In a cross-sectional view in the thickness direction T, the interface 13 has an irregular wavy curve. The interface 13 is also the top surface 32 of the low-density foam layer 30 and the bottom surface 41 of the high-density foam layer 40 (see Figure 2).

[0015] The high-density foam layer 40 is formed by heating and compressing either the top or bottom surface of a low-density foam having approximately the same density as the low-density foam layer 30, thereby increasing the density of that side. The manufacturing method of the soundproofing member 10 in this embodiment includes the step of heating and compressing one side of the foam to increase its density.

[0016] In this process, the heating temperature is, for example, around 160°C to 200°C, preferably 170°C to 190°C, and the compression time is, for example, around 20 seconds to 120 seconds, preferably 30 seconds to 100 seconds.

[0017] The soundproofing member 10 is not constructed by bonding a low-density foam layer 30 and a high-density foam layer 40 together, but rather by integrating them at the interface 13. Furthermore, the low-density foam layer 30 and the high-density foam layer 40 are composed of the same material and are chemically identical. Therefore, the high-density foam layer 40 and the low-density foam layer 30 can be made from a single foam material, making manufacturing rational and preventing delamination at the interface between them. However, the two layers have different cellular pore structures and thus have different physical properties.

[0018] The thickness of the low-density foam layer 30 is, for example, about 5 to 20 mm, which corresponds to about 70% to 95% of the thickness of the soundproofing material 10 (for example, 8 to 25 mm). The thickness of the high-density foam layer 40 is, for example, about 0.8 mm to 3 mm, which corresponds to about 5% to 30% of the thickness of the soundproofing material 10.

[0019] The soundproofing member 10 according to this embodiment has breathability throughout its entire thickness direction T. The breathability of the soundproofing member 10 is measured by JIS L 1096 Method A (Fragile method), for example, 0.1 to 3 cm. 3 / (cm 2·s), preferably 0.1 to 2 cm 3 / (cm 2 ·s), more preferably 0.1 to 1 cm 3 / (cm 2 ·s). The density of the low-density foam layer 30 is 60 to 170 kg / m 3 and the density of the high-density foam layer 40 is 250 to 800 kg / m 3 .

[0020] The material of the sound insulation member 10 is a resin foam, for example, a polyurethane foam.

[0021] <Example> The invention according to this embodiment will be described below with specific examples.

[0022] FIG. 3 is a schematic diagram of a manufacturing method of the sound insulation member 10. As shown in FIG. 3, in this embodiment, first, a polyurethane foam as the foam 50 before compression molding is manufactured by mold molding. The foam 50 has a flat plate shape with a thickness of 20 mm. The density of the foam 50 is 100 kg / m 3 .

[0023] The foam 50 is heated and compressed from above by a hot press machine and molded. The upper mold 62 of the press machine is heated and moves toward the lower mold 61, and the foam 50 is compressed. At this time, the foam 50 is heated at 180° C. for 60 seconds, and the foam 50 is compressed from 20 mm to 3 mm using a 3-mm spacer 66.

[0024] Since the foam 50 is an elastic body, at room temperature, even if it is compressed, it will return to its original thickness when the pressure is released. However, in this embodiment, during heat compression, one side, that is, one side is heated and compressed by the upper mold 62 of the hot press machine, while the other side is compressed at room temperature by the lower mold 61 of the hot press machine. Therefore, since heat is transferred from the one side heated by the upper mold 62, only the part where the heat is transferred undergoes plastic deformation and is shaped in a compressed state.

[0025] After heating and compression, when the pressure is released, the heated side of the foam 50 (the side facing the upper die 62 of the hot press) maintains its shape, while the unheated side of the foam 50 (the side facing the lower die 61 of the hot press) returns to its original shape. In this way, a soundproofing member 10 with a thickness of 12 mm, having a low-density foam layer 30 and a high-density foam layer 40, is obtained. The basis weight, which is the mass per unit area, is 2.0 kg / m². 2 That is the case.

[0026] Figure 4 is an enlarged cross-sectional photograph (50x magnification) of a soundproofing member 10 according to an embodiment of the present disclosure. As shown in Figure 4, a low-density foam layer 30 with a round cell shape is formed on the lower side of the photograph, and a high-density foam layer 40 with smaller cells is formed adjacent to the low-density foam layer 30 on the upper side of the photograph. An irregular wavy boundary surface 13 is formed at the boundary between the low-density foam layer 30 and the high-density foam layer 40 (white double line in Figure 4).

[0027] When the foam 50 (see Figure 3) is heated and compressed, the upper surface 42 of the high-density foam layer 40, which is closer to the heat source, becomes hotter, and more heat is transferred, causing the cells of the foam 50 to deform. On the other hand, heat is not easily transferred and deformation is difficult near the interface 13 of the high-density foam layer 40. This heat transfer characteristic and thermal deformability are related to the cell structure, and the interface 13 has an irregular wavy curve. As a result, sound generated from a noise source is absorbed by the low-density foam layer 30, and then incident on the irregular wavy interface 13, where it is randomly reflected and transmitted.

[0028] The cell shape and cell size of the low-density foam layer 30 are approximately the same as those of the cross-section of the polyurethane foam, which is the foam 50, before compression molding. Therefore, the density of the low-density foam layer 30 is approximately 100 kg / m³, the same as before compression molding. 3 Furthermore, the cell shape within the low-density foam layer 30 is round, and the cell diameter is 100 μm to 300 μm. The thickness of the low-density foam layer 30 is approximately 10 mm, which is the thickness of the soundproofing material 10 minus the thickness of the high-density foam layer 40.

[0029] The cell shape of the high-density foam layer 40 is small and compressed. Furthermore, the cell size of the high-density foam layer 40 is mostly 50 μm or less, which is smaller than that of the low-density foam layer 30. The thickness of the high-density foam layer 40 is approximately 2 mm. The density of the high-density foam layer 40 is approximately 500 kg / m³. 3 It is presumed that...

[0030] Here, the cell structure of a foam is typically as follows: The bubbles within a cell are surrounded by multiple cell walls (cell membranes) that enclose them. If there are, for example, 6 to 20 cell walls, the cell structure is a polyhedron, such as a hexahedron or icosahedron. The cell walls are usually called cell membranes and have a very thin film thickness. Some cell membranes may be partially or completely torn. The cell skeleton is located between adjacent cell walls and corresponds to the edges in a polyhedron. One cell wall (cell membrane) is surrounded by the skeletons of multiple cells, and one cell is formed by multiple cell walls (cell membranes) and multiple cell skeletons that surround it.

[0031] The cell skeleton is the structure that supports the cells and cell membranes, and plays a role in maintaining the overall shape and stability of the foam. The cell skeleton affects the rigidity and durability of the foam. A strong cell skeleton makes it easier for the foam to maintain its shape.

[0032] Normally, bubbles grow inside a foam, and the foam is formed by containing a large number of bubbles. For this reason, in a typical foam, the cross-section of the cell shape is generally circular or elliptical. The cell shape in the low-density foam layer 30 of this embodiment is also generally circular or elliptical, as shown in Figure 4.

[0033] Figure 5 is an enlarged cross-sectional photograph of a high-density foamed layer 40 according to an embodiment of the present disclosure. As shown in Figure 5, the cells of the high-density foamed layer 40 are crushed by the heat compression by the hot press machine described above, and the cell skeletons themselves are crushed, buckled, and deformed. As a result, the cells themselves are slightly deformed, and the cross-sectional shape of the cells is also greatly crushed and deformed. The rounded arcs of the cells have disappeared, and in places the cell skeletons have buckled inward, causing them to bend significantly. However, although the cells are deformed, the cell skeletons themselves still exist, and there are also cells (voids) surrounded by multiple cell skeletons. The inside of the voids is empty space, and gas flows through this area.

[0034] No heat-melted film layer is formed on the heated and compressed surface of the foam 50. In the high-density foam layer 40, the cells are crushed and densely packed together while maintaining the buckled cell skeleton. The high-density foam layer 40 of the soundproofing member 10 in this embodiment has a cell skeleton.

[0035] Figure 6 is a schematic diagram showing the cell size of the high-density foam layer 40 in the thickness direction T. As shown in Figure 6, the cell size (pore diameter) of the high-density foam layer 40 differs depending on the position in the thickness direction T. Specifically, the cell size (pore diameter) on the upper surface 42 side of the high-density foam layer 40 (the second surface 12 side of the soundproofing member 10) is smaller than the cell size (pore diameter) on the interface surface 13 side of the high-density foam layer 40. In other words, the cell size (pore diameter) of the high-density foam layer 40 is smaller on the opposite side of the low-density foam layer 30 than on the low-density foam layer 30 side in the thickness direction T. Thus, the high-density foam layer 40 has different cell sizes in the thickness direction T, making it a so-called gradient material. Here, a gradient material is a material in which the composition and function change continuously or stepwise within a single material. In the soundproofing member 10 configured in this way, noise from the low-density foam layer 30 side is attenuated by the low-density foam layer 30 with larger cell sizes, and then sound is insulated by the high-density foam layer 40 with smaller cell sizes.

[0036] The cell shape in the high-density foam layer 40 is complex and irregular. Therefore, the cell size of such irregularly shaped cells (pores) is determined as follows.

[0037] Specifically, each cell existing in a certain visual field obtained from a certain projection image (Fig. 5) is drawn in an elliptical shape, paying attention to the approximate size (major axis a and minor axis b) of the cell while ignoring the concavities and convexities of the cell contour to some extent. The length of the major axis of the ellipse approximated in this way is obtained as the major axis a, and the length of the minor axis of the ellipse is obtained as the minor axis b.

[0038] Also, the aspect ratio AR is the ratio of the major axis a to the minor axis b of the cell (AR = b / a). The aspect ratio AR takes values in the range of 0 < AR ≤ 1. The smaller the aspect ratio AR, the flatter the cell shape indicates.

[0039] On average, the cell size of the high-density foam layer 40 shown in Fig. 6 is smaller on the upper surface 42 side of the high-density foam layer 40 on the opposite side of the low-density foam layer 30 than on the low-density foam layer 30 side in the thickness direction T.

[0040] The comparison of cell sizes can be obtained as follows. In a certain projection image (for example, Fig. 5), about 5% of the upper end side and about 5% of the lower end side where cells are difficult to observe are cut off, and a rectangular full-image area where all cells can be observed is partitioned within the area. When the lower surface and the upper surface of this full-image area are set to 0% and 100% respectively in the thickness direction T, the full-image area is partitioned into a first small-image area occupying the range of 15% - 25% in the thickness direction T and a second small-image area occupying the range of 75% - 85% in the thickness direction T. Note that the first small-image area and the second small-image area respectively correspond to the projection of the first area T20 and the second area T80 shown in Fig. 6. Next, each cell within the range of each small-image area is drawn in an elliptical shape, paying attention to the approximate size (major axis a and minor axis b) of the cell (pore). Then, the cell size is obtained with the length of the major axis of the ellipse as the major axis a and the length of the minor axis of the ellipse as the minor axis b. Note that cells that protrude more than half into each small-image area are excluded from the target.

[0041] The comparison of cell sizes in the thickness direction T is performed by calculating the arithmetic mean diameter of the major axis a and minor axis b of each cell in each small image region and comparing the arithmetic mean diameters in each small image region.

[0042] Figure 7 is a photograph of the bottom surface 31 of the low-density foam layer 30 when the soundproofing member 10 is viewed from the first surface 11 side. As shown in Figure 7, cells with a cell size of 100 to 500 μm are present on the bottom surface 31 of the low-density foam layer 30.

[0043] Figure 8 is a photograph of the upper surface 42 of the high-density foam layer 40 when the soundproofing member 10 is viewed from the second surface 12 side. As shown in Figure 8, on the upper surface 42 of the high-density foam layer 40, although the size of the cells or pores (cell size) is small, less than 100 μm, there are pores with open cell windows (cell membranes).

[0044] <Comparative Example> For comparison, the sound insulation and sound absorption properties of the example were evaluated in comparison with the comparative example below.

[0045] • Comparative Example 1: Comparative Example 1 used a polyurethane foam molded into a flat sheet with a thickness of 20 mm, which was the same material used in the example. The density of this polyurethane foam was 100 kg / m³. 3 Therefore, the mass per unit area is 2.0 kg / m². 2 That is the case. Comparison Example 2: A polyurethane foam molded into a flat plate with a thickness of 10 mm, and having a density of 200 kg / m³. 3 Therefore, the mass per unit area is 2.0 kg / m². 2 The following was used as Comparative Example 2. Comparison Example 3: Comparative Example 3 was created by cutting the polyurethane foam used in Comparative Example 1 into a flat sheet with a thickness of 10 mm and bonding TPO (thermoplastic olefinic elastomer) to the cut surface with adhesive. Here, the TPO (thermoplastic olefinic elastomer) was in the form of a 2 mm thick sheet with a basis weight of 900 kg / m². 2 Therefore, the mass per unit area is 2.8 kg / m². 2 That is the case.

[0046] <Breathability> The soundproofing member 10 according to the embodiment of this disclosure comprises a low-density foam layer 30 and a high-density foam layer 40. The permeability of the soundproofing member 10 including the low-density foam layer 30 and the high-density foam layer 40 over the entire thickness direction T is 0.3 to 0.5 cm. 3 / (cm 2 ·s) is (JIS L 1096 Method A (Fragile Method)).

[0047] The high-density foam layer 40 has pores that, although small, contain spaces between cells. Since these pores are connected from the low-density foam layer 30 to the high-density foam layer 40 in the thickness direction T, it has breathability throughout its entire thickness.

[0048] On the other hand, the air permeability of Comparative Example 1 was 0.3-0.5 cm. 3 / (cm 2 ·s). The air permeability of Comparative Example 2 is 3-10 cm. 3 / (cm 2 ·s). The air permeability of Comparative Example 3 is 0cm 3 / (cm 2 ·s) and lacks breathability.

[0049] <Transmission loss> Sound insulation tests were conducted in an acoustic evaluation room where an anechoic chamber was placed above a reverberation chamber. Figure 9 shows the transmission loss test data for the example and comparative example. The test method and conditions are as follows.

[0050] A 0.8 mm thick steel plate is placed on the wall between the reverberation chamber and the anechoic chamber. The soundproofing member 10 is placed on the steel plate with the low-density foam layer 30 on the bottom and the high-density foam layer 40 on top. The sample size is 500 x 500 mm x thickness t.

[0051] A speaker was vibrated in a reverberation chamber to generate noise, and the sound pressure level was measured using a microphone placed at a distance from the steel plate. In addition, five microphones were arranged on the anechoic chamber side and placed 50 mm away from the top surface of the sample.

[0052] Sound insulation performance was calculated using the following formula 1, in accordance with "SAE J1400". Equation 1: TL (Transmission Loss) = (SPL1) - (SPL2) - Correction Value Here, SPL1 = Sound pressure level in a reverberation chamber (dB) SPL2 = Sound pressure level in an anechoic chamber (dB) Correction value = MNR (standard sample) - TL theoretical value (standard sample) MNR (Standard Sample) = SPL1 (Standard Sample) - SPL2 (Standard Sample) Standard sample: 0.8mm steel plate Here, the terms are defined as follows: MNR...Measured Noise Reduction TL...Transmission Loss

[0053] As shown in Figure 9, the example demonstrated significantly better performance than Comparative Examples 1 and 2, and was nearly equivalent to or slightly superior to Comparative Example 3 in the frequency range below 4000 Hz. While transmission loss is greatly influenced by mass, the basis weight of the example was 2.0 kg / m². 2 Therefore, the basis weight of Comparative Example 3 is (2.8 kg / m 2 Despite being smaller, it was found to have equivalent or better performance.

[0054] <Insertion Loss> Figure 10 shows the insertion loss test data for the example and comparative examples. In Figure 10, the insertion loss is calculated by subtracting the transmission loss of the steel plate from the transmission loss. Insertion loss represents the pure sound insulation effect. The example performed far better than comparative examples 1 and 2, and was almost equivalent to or slightly better than comparative example 3 in the frequency range below 4000 Hz. Transmission loss is greatly affected by mass, but the basis weight of the example was 2.0 kg / m. 2 Therefore, the basis weight of Comparative Example 3 is (2.8 kg / m 2 Despite being smaller, it was found to have equivalent or better performance.

[0055] <Sound absorption coefficient> Figure 11 shows the test data for the normal incidence sound absorption coefficient in the example and comparative example. Figure 11 shows the measurement data for the normal incidence sound absorption coefficient (according to JIS A1405-2:2007:1998) for the center frequency of the 1 / 3 octave band. The example has a high sound absorption coefficient of 50% or more in the mid-to-low frequency range of 1000Hz to 2000Hz, demonstrating excellent sound absorption.

[0056] According to this disclosure, the soundproofing member 10 of the present invention has a multi-layer structure in which a high-density foam layer 40 is supported by a lighter low-density foam layer 30, and therefore has excellent sound insulation and sound absorption properties. More specifically, if the soundproofing member 10 is positioned to cover the noise source, the low-density foam layer 30 is positioned on the sound source side, and the high-density foam layer 40 is positioned on the opposite side. As a result, the noise from the noise source side is absorbed by the low-density foam layer 30 and then sound-insulated by the high-density foam layer 40. Therefore, the soundproofing member 10 according to this embodiment can achieve both sound insulation and sound absorption performance. Soundproofing materials can reduce noise generated from noise sources such as power units and can be used in the engine compartments and dashboards of vehicles and heavy machinery. They can also be used as soundproof covers for motors, compressors, and other noise sources, as well as soundproof floors to insulate the interior from the exterior.

[0057] Although the present disclosure has described the embodiments described above, it is not limited to these embodiments, and various modifications are possible without departing from the spirit of the invention. In particular, the configurations described herein can be combined as needed. [Explanation of Symbols]

[0058] 10 Soundproofing materials 11 1st side...Bottom side, sound source side 12. Second surface... Top side (front side)... (opposite side of the first surface) 13. Interface H horizontal direction W (width direction) T thickness direction T20 1st area T80 2nd area 30 Low-density foam layer 31 Bottom surface of the low-density foam layer 32 Top surface of the low-density foam layer 40 High-density foam layer 41. Bottom surface of the high-density foam layer 42 Top surface of the high-density foam layer 50 Foam before compression molding 61 Lower die of press machine 62 Upper die of press machine 66 Spacers

Claims

1. Low-density foam layer, The low-density foam layer comprises a high-density foam layer disposed on one side in the thickness direction of the low-density foam layer, and having a higher density than the low-density foam layer. The aforementioned high-density foam layer maintains its framework, The low-density foam layer and the high-density foam layer are breathable throughout the entire thickness direction. Soundproofing material.

2. The cell size of the high-density foam layer is greater than that of the low-density foam layer in the thickness direction. The opposite side of the aforementioned low-density foam layer is smaller. The soundproofing member according to claim 1.

3. The interface between the low-density foam layer and the high-density foam layer has an irregular wavy curve when viewed in cross-section in the thickness direction. The soundproofing member according to claim 1.

4. The breathability of the soundproofing material is 0.1 to 1 cm. ３ / cm ２ / s is The soundproofing member according to claim 1.

5. A method for manufacturing a soundproofing member according to any one of claims 1 to 4, The process includes heating and compressing one side of the foam to increase the density of that side. A method for manufacturing soundproofing materials.

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