Soundproof material for vehicle

Abstract

This soundproof material (3) for a vehicle comprises a polyurethane foam (30) having, in the thickness direction, a front layer (400) including a front surface, a back layer (401) including a back surface, and an intermediate layer (402) disposed between the front layer (400) and the back layer (401). The thickness of the polyurethane foam (30) is 5-17.5 mm, and the tensile strength of the polyurethane foam (30) is 700-1480 kPa. The normal incidence sound absorption coefficient of the polyurethane foam (30) at a frequency of 5000 Hz, as measured using a disk-shaped sample having a diameter of 30 mm, is 0.34 or more.

Description

Soundproofing material for vehicles

[0001] This disclosure relates to soundproofing materials for vehicles, such as those used in the engine compartment of a vehicle.

[0002] In vehicles such as automobiles, various measures are taken to reduce noise leaking outside the vehicle or into the passenger compartment. For example, in the engine compartment of a vehicle, soundproofing materials such as engine covers, side covers, and oil pan covers are placed around the engine to reduce the noise radiated from the engine, which is the source of the noise. This type of soundproofing material, as described in Patent Document 1, for example, consists of a rigid cover member made of resin or the like and a soft polyurethane foam placed on its back side, and is attached to the mating member (noise source) by fastening the cover member with bolts or the like.

[0003] Japanese Patent Publication No. 2004-44526, Japanese Patent Publication No. 2024-14696, International Publication No. 2024 / 024845, Japanese Patent Publication No. 2024-094079

[0004] Generally, flexible polyurethane foam has high breathability and sound absorption properties, but its low rigidity makes it unsuitable for independent use. Therefore, considering factors such as ease of attachment to mating components, it is often used in conjunction with rigid cover components. However, using cover components increases mass and cost. Furthermore, the increased thickness makes application in confined spaces difficult. In vehicle engine compartments, the target for reduction is not only radiated noise from noise sources but also reverberating noise within the space. However, if cover components are placed on the passenger compartment side, the sound absorption against reverberating noise from the passenger compartment side decreases.

[0005] For example, Patent Document 2 specifies that the thinnest part thickness is 5.0 to 50 mm, the Asker C hardness is 20 to 100 points, the average sound absorption coefficient (JIS A1405-2:2007) at 1000 to 3500 Hz is 0.6 or higher, the average sound absorption coefficient at 1000 to 2000 Hz is 0.5 or higher, and the air permeability is 0.1 to 100 cm. ３ / cm ２A flexible polyurethane foam with a density of / sec is described. Patent document 3 describes a lightweight polyurethane foam with an average sound transmission loss (JIS A1441-1:2007) of 30 dB or more at frequencies of 1000 to 6300 Hz and an Asker C hardness of 30 or less. Patent document 4 describes a polyurethane foam in which the density of a first portion 2 mm from the outside is greater than the density of a second portion 2 mm inside, with a tensile strength of 476 to 558 kPa, a frequency at which the reverberation chamber sound absorption coefficient (JIS A1409) shows a peak of 2000 Hz or less, and a reverberation chamber sound absorption coefficient of 0.70 or more at 1000 Hz.

[0006] In electric vehicles, which have become increasingly popular in recent years, sound absorption in the high-frequency range of around 5000 Hz generated by motors and other components is required. However, conventional polyurethane foam does not have sufficient sound absorption in the high-frequency range. Furthermore, paragraph

[0039] of Patent Document 2 describes that by incorporating a foam-breaking agent to coarseen the cells, the average sound absorption coefficient in a specific frequency range can be increased. However, increasing the cell diameter shortens the sound propagation path, which reduces sound absorption in the low-frequency range below 1000 Hz.

[0007] This disclosure has been made in view of the above circumstances, and aims to provide a soundproofing material for vehicles comprising a polyurethane foam that has the desired rigidity on its own and excellent sound absorption in the high-frequency range.

[0008] (1) The soundproofing material for vehicles according to the present disclosure is a soundproofing material for vehicles comprising polyurethane foam, wherein the polyurethane foam has, in the thickness direction, a surface layer including the surface, a back layer including the back surface, and an intermediate layer disposed between the surface layer and the back layer, the thickness of the polyurethane foam is 5 mm or more and 17.5 mm or less, the tensile strength of the polyurethane foam is 700 kPa or more and 1480 kPa or less, and the normal incidence sound absorption coefficient of the polyurethane foam at a frequency of 5000 Hz, measured using a disc-shaped sample with a diameter of 30 mm, is 0.34 or more.

[0009] The polyurethane foam constituting the soundproofing material for vehicles of this disclosure (hereinafter sometimes referred to as "the polyurethane foam of this disclosure") has at least three layers in the thickness direction: a surface layer, an intermediate layer, and a back layer. Due to the high tensile strength of the polyurethane foam of this disclosure, the desired rigidity can be achieved with a single material. The normal incidence sound absorption coefficient is an indicator of sound absorption, and a higher normal incidence sound absorption coefficient indicates higher sound absorption. The polyurethane foam of this disclosure is particularly excellent in sound absorption in the high-frequency range, including 5000 Hz. For example, increasing the density of the entire polyurethane foam to make it harder may increase its rigidity, but the air layer decreases, thus reducing its sound absorption. In the polyurethane foam of this disclosure, the surface layer, intermediate layer, and back layer are laminated in the thickness direction, achieving both rigidity and sound absorption.

[0010] As mentioned above, in a vehicle's engine compartment, not only radiated noise from noise sources but also reverberating noise within the space needs to be reduced. The polyurethane foam of this disclosure has the desired rigidity and can be used alone without support from rigid cover members. In this case, sound absorption is exhibited on both sides of the polyurethane foam (the side facing the noise source and the opposite side), further improving its effectiveness as a soundproofing material. Furthermore, by not using rigid cover members, the soundproofing material for vehicles of this disclosure can be made lighter and less expensive, and can be fixed to the mating member using a simple method such as clips. In addition, because the polyurethane foam of this disclosure is relatively thin, it is easy to apply to narrow spaces.

[0011] (2) In the above configuration, the normal incidence sound absorption coefficient of the polyurethane foam at a frequency of 800 Hz, measured using a disc-shaped sample with a diameter of 30 mm, may be 0.14 or higher. Increasing the thickness of the polyurethane foam may improve the sound absorption in the low frequency range of about 800 to 1000 Hz. However, in the polyurethane foam of this disclosure, the sound absorption in the low frequency range is enhanced by arranging three layers, "surface layer / intermediate layer / back layer," in the thickness direction while keeping the thickness relatively small. With this configuration, high sound absorption can be achieved in both the low frequency range and the high frequency range.

[0012] (3) In any of the above configurations, the normal incidence transmission loss of the polyurethane foam at a frequency of 5000 Hz, measured using a disc-shaped sample with a diameter of 30 mm, may be 23.00 dB or more. Normal incidence transmission loss is an indicator of sound insulation performance, and a larger normal incidence transmission loss indicates higher sound insulation performance. This configuration makes it possible to achieve high sound absorption and sound insulation in the high-frequency range.

[0013] (4) In the configuration of (3) above, the normal incidence transmission loss of the polyurethane foam at a frequency of 800 Hz, measured using a disc-shaped sample with a diameter of 30 mm, may be 14.82 dB or more. With this configuration, high sound insulation can be achieved in both the low-frequency and high-frequency ranges.

[0014] The soundproofing material for vehicles disclosed herein has the desired rigidity and excellent sound absorption in the high-frequency range. Because the soundproofing material for vehicles disclosed herein has a relatively small thickness, it can be applied to confined spaces. The soundproofing material for vehicles disclosed herein can contribute to weight reduction and cost reduction.

[0015] This is a graph of the normal incidence sound absorption coefficient of the polyurethane foam of Examples 1 to 3. This is a graph of the normal incidence sound absorption coefficient of the polyurethane foam of Examples 4 to 8. This is a graph of the normal incidence sound absorption coefficient of the polyurethane foam of Comparative Examples 1 to 4. This is a graph of the normal incidence transmission loss of the polyurethane foam of Examples 1 to 3. This is a graph of the normal incidence transmission loss of the polyurethane foam of Examples 4 to 8. This is a graph of the normal incidence transmission loss of the polyurethane foam of Comparative Examples 1 to 4. This is a perspective view of the soundproofing material for vehicles according to the first embodiment. This is an unfolded view of the soundproofing material for vehicles. This is a cross-sectional view in the IX-IX direction of Figure 8.

[0016] The embodiments of the soundproofing material for vehicles described herein will be described below. However, the embodiments are not limited to those described below, and can be implemented in various modified and improved forms as possible for those skilled in the art. In this specification, numerical ranges using "~" indicate a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described stepwise in this specification, the individually described upper and lower limits can be combined arbitrarily. Furthermore, the upper and lower limits of the numerical ranges can be replaced with the values ​​shown in the examples.

[0017] In the soundproofing material for vehicles disclosed herein, the composition other than polyurethane foam is not particularly limited. The soundproofing material for vehicles disclosed herein may consist solely of polyurethane foam, or it may be composed of polyurethane foam in combination with other materials. For example, when the soundproofing material for vehicles disclosed herein is implemented in an engine cover, the engine cover may be a single-layer structure of polyurethane foam, or a multi-layer structure having a soundproofing layer made of polyurethane foam and a surface layer covering it. The surface layer may be formed using resin, elastomer, metal, fiber, etc. Furthermore, the term "vehicle" as an application includes not only automobiles but also airplanes, trains, etc. The polyurethane foam constituting the soundproofing material for vehicles disclosed herein will be described below.

[0018] <Structure of Polyurethane Foam> The polyurethane foam has, in the thickness direction, a surface layer including the surface, a back layer including the back surface, and an intermediate layer disposed between the surface layer and the back layer. The thickness of each of the surface layer, intermediate layer, and back layer is not particularly limited. The thickness of the polyurethane foam is 5 mm or more and 17.5 mm or less. The thickness of the polyurethane foam may be adjusted as appropriate depending on the application. The soundproofing material for vehicles of this disclosure has a relatively small thickness of polyurethane foam, making it easy to apply to the narrow spaces of vehicles. The thickness of the polyurethane foam may be constant or may vary by forming irregularities. For example, a thin-walled section with a smaller thickness than other parts can be formed in the shape of a groove, and this thin-walled section can function as a hinge. In this case, the polyurethane foam can be curved with the thin-walled section as an axis and attached to conform to the shape of the mating member. As a result, the coverage rate of the mating member can be increased, and the soundproofing effect can be enhanced.

[0019] <Physical Properties and Characteristics of Polyurethane Foam> [Tensile Strength] The tensile strength of the polyurethane foam of this disclosure is 700 kPa or more and 1480 kPa or less. If the tensile strength is less than 700 kPa, sufficient rigidity cannot be obtained. A more suitable tensile strength is 800 kPa or more. On the other hand, if it is greater than 1480 kPa, the sound absorption decreases. A more suitable tensile strength is 1200 kPa or less. The tensile strength in this disclosure is the tensile strength at break (TS) measured by a tensile test in accordance with JIS K6251:2023. ｂ ) The test specimen shall be a dumbbell-shaped No. 1.

[0020] [Normal Incidence Sound Absorption Coefficient] In this disclosure, the normal incidence sound absorption coefficient is the value obtained by measuring a disc-shaped sample with a diameter of 30 mm using the method described in JIS A1405-2:2007. The thickness of the disc-shaped sample used is the same as the thickness of the polyurethane foam being measured. The normal incidence sound absorption coefficient of the polyurethane foam in this disclosure is 0.34 or higher at a frequency of 5000 Hz in the high frequency range. It is more preferable to have a value of 0.40 or higher. In the low frequency range of 800 Hz, it is 0.14 or higher. It is more preferable to have a value of 0.19 or higher. The normal incidence sound absorption coefficient is 0.34 or higher at a frequency of 5000 Hz, and may be less than 0.14 at a frequency of 800 Hz, but it is desirable to satisfy 0.14 or higher and 0.34 or higher at 800 Hz and 5000 Hz, respectively. It is also preferable to have a value of 0.14 or higher in the frequency range between these two frequencies (800 Hz to 5000 Hz). Furthermore, it is desirable that the value be 0.34 or higher even in the high-frequency range beyond 5000 Hz up to 6300 Hz.

[0021] [Normal incidence transmission loss] In this disclosure, the normal incidence transmission loss is defined as the value measured using a 30 mm diameter disc-shaped sample by the method described in ASTM E 2611. The thickness of the disc-shaped sample used is the same as the thickness of the polyurethane foam being measured.

[0022] The normal incidence transmission loss of the polyurethane foam disclosed herein is 23.00 dB or more at a frequency of 5000 Hz in the high frequency region. It is more preferable that it be 24.00 dB or more. At a frequency of 800 Hz in the low frequency region, it is 14.82 dB or more. It is more preferable that it be 17.00 dB or more. It is desirable that the normal incidence transmission loss satisfies either 14.82 dB or more at 800 Hz or 23.00 dB or more at 5000 Hz, but it is more preferable that it satisfies 14.82 dB or more and 23.00 dB or more at 800 Hz and 5000 Hz, respectively. It is also preferable that it be 14.82 dB or more in the frequency region between these two frequencies (800 Hz to 5000 Hz). Furthermore, it is preferable that it be 23.00 dB or more in the high frequency region from 5000 Hz up to 6300 Hz.

[0023] [Density] The overall density of the polyurethane foam of the present disclosure is 150 kg / m ３ or more and 1000 kg / m ３ or less, which is preferable. When the density is less than 150 kg / m ３ , it becomes difficult to obtain desired rigidity. A more preferred density is 160 kg / m ３ or more. On the other hand, when the density exceeds 1000 kg / m ３ , the proportion of air space decreases, resulting in reduced sound absorption. A more preferred density is 700 kg / m ３ or less, even more preferably 500 kg / m ３ or less. In the present disclosure, the value calculated by dividing the mass of the polyurethane foam to be measured by its volume is adopted as the overall density.

[0024] <Method for Producing Polyurethane Foam> The polyurethane foam of the present disclosure may be produced by foam-molding a urethane foam resin raw material composed of an isocyanate component, a polyol component, a catalyst, a blowing agent and the like. In foam molding, the urethane foam resin raw material is injected into a molding die, and a foaming reaction and a curing reaction are allowed to proceed at a temperature of about 40 to 100°C. Then, before the curing reaction is completed, the urethane foam resin raw material is compressed in the front-back direction, whereby a polyurethane foam having a front layer, a back layer, and an intermediate layer disposed therebetween can be produced. The compression ratio [(thickness before compression − thickness after compression) / thickness before compression × 100] is preferably set to 10 to 50%. Further, the cell structure of the front layer and the back layer may be adjusted by performing crushing using a roll or the like after foam molding.

[0025] The isocyanate component is not particularly limited as long as it forms a urethane bond through reaction with the polyol component. For example, it can be appropriately selected from tolylene diisocyanate (TDI), phenylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate (NDI), and their derivatives. Examples of derivatives include prepolymers obtained by the reaction of isocyanate and polyol, modified polyisocyanates, and polymeric MDI (multinuclear) having three or more isocyanate groups and benzene rings in one molecule.

[0026] The polyol component can be appropriately selected from among polyhydric hydroxy compounds, polyether polyols, polyester polyols, polymer polyols, polyether polyamines, polyester polyamines, alkylene polyols, urea-dispersed polyols, melamine-modified polyols, polycarbonate polyols, acrylic polyols, polybutadiene polyols, phenol-modified polyols, and others.

[0027] Examples of catalysts include amine catalysts such as tetraethylenediamine, triethylenediamine, and dimethylethanolamine, as well as organometallic catalysts such as tin laurate and tin octanoate. Examples of blowing agents include water, methylene chloride, chlorofluorocarbons, and CO2. ２ Examples include gas.

[0028] The foamed urethane resin raw material may further contain foam stabilizers, plasticizers, crosslinking agents, chain extenders, flame retardants, antistatic agents, viscosity reducers, stabilizers, fillers, colorants, etc. Examples of foam stabilizers include silicone-based foam stabilizers. Examples of crosslinking agents include diethylene glycol, triethanolamine, and diethanolamine. Examples of flame retardants include expanded graphite, phosphorus-based, halogen-based, and metal hydroxide-based flame retardants.

[0029] The foamed urethane resin raw material is preferably prepared by adding the isocyanate component to a premixed polyol, which is made by pre-mixing components other than the isocyanate component with the polyol component. In this case, the premixed polyol and the isocyanate component may be mechanically stirred using a propeller or the like, or they may be mixed by discharging the premixed polyol and the isocyanate component separately at high pressure using a high-pressure injector or the like, causing the two components to collide. It is desirable that the premixed polyol and the isocyanate component be blended so that the isocyanate index (equivalents of isocyanate groups / equivalents of active hydrogen groups × 100) is between 100 and 150, preferably between 100 and 120.

[0030] <First Embodiment> An embodiment of the soundproofing material for vehicles of the present disclosure will be described with reference to the drawings. [Configuration] First, the configuration of the soundproofing material for vehicles of this embodiment will be described. Figure 7 shows a perspective view of the soundproofing material for vehicles of this embodiment. Figure 8 shows an unfolded view of the soundproofing material for vehicles. Figure 9 shows a cross-sectional view of Figure 8 in the IX-IX direction. In Figure 8, for the sake of explanation, the thin-walled portion is shown by a dashed line. As shown in Figures 7 and 8, the soundproofing material for vehicles 3 has a rectangular box shape and covers the entire mating member (noise source) which is not shown. The soundproofing material for vehicles 3 is made of polyurethane foam 30. The polyurethane foam 30 has eleven main body portions 40a to 40k and thin-walled portions 41 arranged between adjacent main body portions.

[0031] The main body sections 40a to 40g constitute the six faces of a rectangular parallelepiped. The thickness of each of the main body sections 40a to 40k is 10 mm. The tensile strength of each of the main body sections 40a to 40k is 1038 kPa.

[0032] The main body portion 40a, which constitutes the upper part of the front surface of the rectangular parallelepiped, has a rectangular parallelepiped-shaped locking projection 42 that protrudes inward. The main body portion 40e, which constitutes the lower part of the front surface of the rectangular parallelepiped, has a locking hole portion 430 into which the locking projection 42 is inserted. The main body portion 40a and the main body portion 40e are fixed together by the insertion of the locking projection 42 into the locking hole portion 430. In addition, the main body portion 40j is connected to the left side of the main body portion 40e, with a thin-walled portion 41 in between, and the main body portion 40k is connected to the right side, with a thin-walled portion 41 in between. Both the main body portions 40j and 40k are in the same small piece shape and are inserted into locking holes 431 and 432, respectively, which will be described later. The main body portion 40f, which constitutes the left side of the rectangular parallelepiped, has a main body portion 40h positioned to the left of it, with a thin-walled portion 41 in between. The main body portion 40h has a locking hole portion 431. The main body portion 40h is bent when attached to the mating member, and the main body portion 40j is inserted through the locking hole portion 431. Similarly, the main body portion 40g, which constitutes the right side of the rectangular parallelepiped, has a main body portion 40i positioned to the right of the thin-walled portion 41. The main body portion 40i has a locking hole portion 432. The main body portion 40i is bent when attached to the mating member, and the main body portion 40k is inserted through the locking hole portion 432.

[0033] The thin-walled section 41 is arranged in a groove-like manner between adjacent main body sections. The thin-walled section 41 is a hinge section that connects adjacent main body sections. The thickness of the thin-walled section 41 is 5 mm, which is thinner than that of the main body sections 40a to 40k. The tensile strength of the thin-walled section 41 is 1476 kPa, which is greater than that of the main body sections 40a to 40k.

[0034] As an example, Figure 9 shows a cross-sectional view in the thickness direction of the main body portion 40d that constitutes the lower surface (bottom surface) of the rectangular parallelepiped. Both the main body portions 40a to 40k and the thin-walled portion 41 have, in the thickness direction, a surface layer 400 including the surface, a back layer 401 including the back surface, and an intermediate layer 402 positioned between the surface layer 400 and the back layer 401. Furthermore, in both the main body portions 40a to 40k and the thin-walled portion 41, when measured using a disc-shaped sample with a diameter of 30 mm, the normal incidence sound absorption coefficient at a frequency of 800 Hz is 0.14 or higher, the normal incidence sound absorption coefficient at a frequency of 5000 Hz is 0.34 or higher, the normal incidence transmission loss at a frequency of 800 Hz is 14.82 dB or higher, and the normal incidence transmission loss at a frequency of 5000 Hz is 23.00 dB or higher.

[0035] After being foam-molded into the developed shape shown in FIG. 8, the polyurethane foam 30 is assembled into a box shape so as to cover the entire mating member (noise source). For example, after placing the mating member on the main body portion 40d, the remaining main body portions 40a to 40c and 40e to 40k are curved inward by approximately 90° (valley-folded) around the thin-walled portion (hinge portion) 41 as a shaft, the small piece-shaped main body portions 40j and 40k are inserted through the locking hole portions 431 and 432, and the locking protrusion 42 is inserted into the locking hole portion 430.

[0036] [Functions and Effects] Next, the functions and effects of the vehicle soundproofing material according to the present embodiment will be described. According to the vehicle soundproofing material 3, the polyurethane foam 30 is integrally foam-molded into a developed shape, and can be easily assembled into a box shape by using the thin-walled portion 41 as a hinge portion. Furthermore, attachment to the mating member can be performed by a simple method of inserting the main body portions 40j and 40k through the locking hole portions 431 and 432, and inserting the locking protrusion 42 into the locking hole portion 430. Since the entire mating member is accommodated inside the vehicle soundproofing material 3, the soundproofing effect can be further enhanced.

[0037] The thickness of the thin-walled portion 41 is smaller than the thickness of the main body portions 40a to 40k, and the tensile strength of the thin-walled portion 41 is higher than the tensile strength of the main body portions 40a to 40k. Therefore, when assembling from a developed shape into a three-dimensional shape, it is easy to bend around the thin-walled portion 41 as a shaft, and the thin-walled portion 41 is less prone to damage. Furthermore, since the tensile strength of the main body portions 40a to 40k is as high as 1038 kPa, desired rigidity can be achieved by the polyurethane foam 30 alone, and the vehicle soundproofing material 3 can be configured. As a result, sound absorption properties are exhibited on both the front and back surfaces of the polyurethane foam 30 (the outer surface and the surface on the mating member side), and not only sound radiated from the mating member but also sound reverberating in the space can be reduced. In addition, since the thickness of the main body portions 40a to 40k is as small as 10 mm, the soundproofing material can be easily applied to narrow spaces. Furthermore, since not only the main body portions 40a to 40k but also the thin-walled portion 41 has high sound absorption and sound insulation properties, the vehicle soundproofing material 3 has a high soundproofing effect.

[0038] Next, the present disclosure will be described more specifically with reference to examples.

[0039] <Manufacturing of Polyurethane Foam> [Examples 1-8] First, 70 parts by mass of polyether polyol (AGC Inc.'s "Exenol® 837") and 30 parts by mass of polymer polyol (Sanyo Chemical Industries, Ltd.'s "Sannix® KC-900") were added as polyol components, 1 part by mass of diethanolamine as a crosslinking agent, 3 parts by mass of water as a blowing agent, 0.3 parts by mass of amine catalyst A (EVONIK's "DABCO® 33LV"), and 0.1 parts by mass of amine catalyst B (MOMENTIVE's "Niax® Catalyst A-1") were added and mixed to prepare a premix polyol. Next, the prepared premixed polyol and polymeric MDI (BASF INOAC Polyurethane Co., Ltd.'s "Luplanate® M20S") as an isocyanate component were mixed to achieve an isocyanate index of 100, thereby preparing a foamed urethane resin raw material.

[0040] Next, a wax-based water-based release agent was applied to the mold surface of the mold, which had been pre-adjusted to 50°C. The foamed urethane resin raw material was then injected into rectangular prism-shaped cavities (500 mm long, 600 mm wide, with three thicknesses: 20 mm, 15 mm, and 10 mm), sealed, and maintained for 1 minute. After that, the mold was opened, a plate (500 mm long, 600 mm wide) was placed on top of the partially cured foamed urethane resin raw material, the mold was clamped again, and maintained for another 3 minutes. At this time, the compression ratio was adjusted by changing the thickness of the plate used. The foam curing reaction was completed while the material was compressed by the plate, and a polyurethane foam was produced having a surface layer including the top surface, a back layer including the bottom surface, and an intermediate layer placed between them. The obtained polyurethane foam was passed between a pair of rolls, and both the top and back surfaces were roll-crushed. In this way, eight types of polyurethane foam with different thicknesses and compression ratios were produced. The produced polyurethane foams are referred to as the polyurethane foams of Examples 1 to 8. The thickness and compression ratio of each polyurethane foam are summarized in Table 1 below. In Table 1, the thickness before compression is the same as the thickness of the mold cavity.

[0041] [Comparative Example 1] The polyurethane foam of Comparative Example 1 was produced in the same manner as in Examples 7 and 8, except that a mold with a cavity thickness of 10 mm was used, the compression ratio by the plate was increased, and the thickness after compression was adjusted to 2.5 mm.

[0042] [Comparative Example 2] The polyurethane foam of Comparative Example 2 was produced in the same manner as in Examples 7 and 8, except that a mold with a cavity thickness of 10 mm was used and no compression was performed using a plate during foam molding. The thickness of the polyurethane foam of Comparative Example 2 is 10 mm.

[0043] [Comparative Example 3] The polyurethane foam of Comparative Example 3 was produced in the same manner as in Comparative Example 2, except that roll crushing was not performed after foam molding. The thickness of the polyurethane foam of Comparative Example 3 is 10 mm.

[0044] [Comparative Example 4] As the polyurethane foam of Comparative Example 4, a polyurethane foam "Calmflex (registered trademark) UGR" (thickness: 10 mm) manufactured by Inoac Corporation was prepared.

[0045]

[0046] <Evaluation of Polyurethane Foam> The tensile strength, density, normal incident sound absorption coefficient, and normal incident transmission loss of the produced polyurethane foam were measured, and the rigidity and sound absorption properties were evaluated.

[0047] [Measurement Method] (1) Tensile Strength A tensile test in accordance with JIS K6251:2023 was performed, and the tensile strength at break (TS ｂ ) was measured. A No. 1 dumbbell-shaped test piece was used, and the tensile speed was set to 200 mm / min.

[0048] (2) Density Density was calculated by dividing the mass of the polyurethane foam by its volume.

[0049] (3) Normal Incident Sound Absorption Coefficient Using a disc-shaped sample with a diameter of 30 mm cut out from the produced polyurethane foam, the normal incident sound absorption coefficient was measured by the method described in JIS A1405-2:2007.

[0050] (4) Normal incidence transmission loss A 30 mm diameter disc-shaped sample cut from the manufactured polyurethane foam was used to measure the normal incidence transmission loss according to the method described in ASTM E 2611.

[0051] [Measurement Results] Table 1, shown above, summarizes the tensile strength and density of the polyurethane foams of the examples and comparative examples. Figure 1 shows a graph of the normal incidence sound absorption coefficient against frequency for the polyurethane foams of Examples 1 to 3. Figure 2 shows a graph of the normal incidence sound absorption coefficient against frequency for the polyurethane foams of Examples 4 to 8. Figure 3 shows a graph of the normal incidence sound absorption coefficient against frequency for the polyurethane foams of Comparative Examples 1 to 4. Figure 4 shows a graph of the normal incidence transmission loss against frequency for the polyurethane foams of Examples 1 to 3. Figure 5 shows a graph of the normal incidence transmission loss against frequency for the polyurethane foams of Examples 4 to 8. Figure 6 shows a graph of the normal incidence transmission loss against frequency for the polyurethane foams of Comparative Examples 1 to 4. In Figures 1 to 3, the points with a sound absorption coefficient of 0.14 at 800 Hz and the points with a sound absorption coefficient of 0.34 at 5000 Hz are indicated by black circles. In Figures 4-6, the points with a transmission loss of 14.82 at 800 Hz and the points with a transmission loss of 23.00 at 5000 Hz are indicated by black circles.

[0052] As shown in Table 1, the polyurethane foams of Examples 1 to 8, with thicknesses of 5 mm to 17.5 mm, had a tensile strength of 708 kPa to 1476 kPa, exhibiting the desired rigidity. Furthermore, as shown in Figures 1 and 2, the normal incidence sound absorption coefficient at 800 Hz was 0.14 or higher, and at 5000 Hz it was 0.34 or higher, confirming high sound absorption in both the low and high frequency ranges. Moreover, as shown in Figures 4 and 5, the normal incidence transmission loss at 800 Hz was 14.82 dB or higher, and at 5000 Hz it was 23.00 dB or higher, confirming high sound insulation in both the low and high frequency ranges.

[0053] In contrast, as shown in Table 1, Figure 3, and Figure 6, the polyurethane foam of Comparative Example 1, with a thickness of 2.5 mm (less than 5 mm), had high tensile strength, but the normal incidence sound absorption coefficient at frequencies of 800 Hz and 5000 Hz was low, and the desired sound absorption could not be obtained in both the low-frequency and high-frequency ranges. The polyurethane foam of Comparative Example 2, which was not compressed during foam molding, had low tensile strength and could not obtain the desired rigidity. Furthermore, the normal incidence transmission loss at frequencies of 800 Hz and 5000 Hz was low, and the desired sound insulation could not be obtained in both the low-frequency and high-frequency ranges. Similarly, the polyurethane foam of Comparative Example 3, which was not compressed during foam molding and did not undergo roll crushing after foam molding, also had low tensile strength and could not obtain the desired rigidity. In the polyurethane foam of Comparative Example 3, the sound insulation was good, but the normal incidence sound absorption coefficient at frequencies of 800 Hz and 5000 Hz was low, and the desired sound absorption could not be obtained in both the low-frequency and high-frequency ranges. In the polyurethane foam of Comparative Example 4, the tensile strength was low and the desired rigidity could not be obtained. Furthermore, the normal incidence sound absorption coefficient was 0.34 or higher at 5000 Hz, but less than 0.14 at 800 Hz, indicating poor sound absorption in the low-frequency range. In addition, the normal incidence transmission loss was low regardless of frequency, indicating poor sound insulation.

[0054] The soundproofing material for vehicles disclosed herein is suitable for use as an eAxle (electric drive module integrating motor, transaxle, and inverter) cover, motor cover, engine cover, timing chain cover, side cover, oil pan cover, inverter cover, compressor cover, dash insulator, floor insulator, rear package tray, wheelhouse liner, and under cover, as well as for use as a soundproofing material placed around the transmission and other components.

[0055] 3: Soundproofing material for vehicles, 30: Polyurethane foam, 40a to 40k: Main body, 41: Thin-walled section, 42: Locking projection, 430, 431, 432: Locking hole section, 400: Surface layer, 401: Back layer, 402: Intermediate layer.

Claims

1. A soundproofing material for vehicles comprising polyurethane foam, wherein the polyurethane foam has, in the thickness direction, a surface layer including the surface, a back layer including the back surface, and an intermediate layer disposed between the surface layer and the back layer, the thickness of the polyurethane foam is 5 mm or more and 17.5 mm or less, the tensile strength of the polyurethane foam is 700 kPa or more and 1480 kPa or less, and the normal incidence sound absorption coefficient of the polyurethane foam at a frequency of 5000 Hz, measured using a disc-shaped sample with a diameter of 30 mm, is 0.34 or more.

2. The soundproofing material for vehicles according to claim 1, wherein the normal incidence sound absorption coefficient of the polyurethane foam at a frequency of 800 Hz, measured using a disc-shaped sample with a diameter of 30 mm, is 0.14 or more.

3. The soundproofing material for vehicles according to claim 1, wherein the normal incidence transmission loss of the polyurethane foam at a frequency of 5000 Hz, measured using a disc-shaped sample with a diameter of 30 mm, is 23.00 dB or more.

4. The soundproofing material for vehicles according to claim 3, wherein the normal incidence transmission loss of the polyurethane foam at a frequency of 800 Hz, measured using a disc-shaped sample with a diameter of 30 mm, is 14.82 dB or more.

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