Soundproofing material for vehicles

Abstract

A sound insulation material for vehicles comprises polyurethane foam. The polyurethane foam has an average pore diameter of 50 μm or more and 200 μm or less, an air resistance of 0.2 kPa·s / m or more and 5 kPa·s / m or less, and an ASKER C hardness of 45 or more. When the perpendicular incident sound absorption coefficient of the polyurethane foam is measured using a circular plate-shaped sample with a diameter of 30 mm and a thickness of 10 mm, the sound absorption coefficient at 800 Hz is 0.30 or more, and the sound absorption coefficient at 5000 Hz is 0.50 or more. This polyurethane foam exhibits desired rigidity and excellent sound absorption in both the low-frequency and high-frequency regions.

Description

Technical Field

[0001] This disclosure relates to sound insulation materials for vehicles used in engine compartments and other areas of vehicles. Background Technology

[0002] In automobiles and other vehicles, various countermeasures are implemented to reduce noise leakage to the outside and inside the vehicle. For example, in the engine compartment of a vehicle, sound-insulating materials such as engine hoods, side covers, and oil pan covers are arranged around the engine to reduce the radiated noise from the engine, which is a noise source. Such sound-insulating materials, for example, as described in Patent Document 1, consist of a rigid cover component made of resin or the like and a soft polyurethane foam disposed on its back side, and are installed on the target component by bolting or other means.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2004-44526; Patent Document 2: Japanese Patent Application Publication No. 2024-14696. Summary of the Invention

[0004] The problem that the invention aims to solve Generally, flexible polyurethane foam has high air permeability and sound absorption, but lacks self-supporting properties due to its low rigidity. Therefore, it is often used with rigid cover components, considering factors such as ease of installation on target components. However, using cover components increases weight and cost accordingly. On the other hand, to give polyurethane foam self-supporting properties and enable it to be used independently, it is considered to harden the polyurethane foam itself. However, hardening the polyurethane foam makes it difficult to connect the cells (bubbles), reducing sound absorption.

[0005] For example, Patent Document 2 describes a thin, wide-frequency sound-absorbing material for vehicles, characterized by an average pore diameter of 2000 μm or more, an ASKER C hardness of 20 to 100, an average sound absorption coefficient of 0.6 or more in the 1000 Hz to 3500 Hz range, an average sound absorption coefficient of 0.5 or more in the 1000 Hz to 2000 Hz range, and an air permeability of 0.1 to 100 cm. 3 / cm 2 / sec of flexible polyurethane foam. As described in paragraph

[0039] of Patent Document 2, the flexible polyurethane foam described in that document is formulated with a predetermined amount of defoaming agent to enlarge the pores, thereby increasing the average sound absorption coefficient in a specific frequency region.

[0006] As described in Patent Document 2, using a defoaming agent to unify tiny pores and increase the pore diameter improves air permeability, thus potentially increasing sound absorption in a specific frequency range. However, increasing the pore diameter shortens the sound propagation path, thereby reducing sound absorption in the low-frequency range below 1000Hz. Furthermore, in the increasingly popular electric vehicles, sound absorption in the high-frequency range of around 5000Hz generated by motors and other components is required.

[0007] This disclosure was made in view of the following actual situation, and its object is to provide a sound insulation material for vehicles using polyurethane foam, said polyurethane foam having the desired rigidity and excellent sound absorption in both the low-frequency and high-frequency regions.

[0008] means for solving problems (1) The vehicle sound insulation material disclosed herein is a vehicle sound insulation material containing polyurethane foam, characterized in that the average cell diameter of the polyurethane foam is 50 μm or more and 200 μm or less, the air resistance is 0.2 kPa·s / m or more and 5 kPa·s / m or less, the ASKER C hardness is 45 or more, and when the vertical incident sound absorption coefficient of the polyurethane foam is measured using a circular plate sample with a diameter of 30 mm and a thickness of 10 mm, the sound absorption coefficient at a frequency of 800 Hz is 0.30 or more, and the sound absorption coefficient at a frequency of 5000 Hz is 0.50 or more.

[0009] To address the aforementioned problems, the inventors conducted extensive research and, by creating a specific cell structure, achieved a balance between rigidity and sound absorption in polyurethane foam. Firstly, in the polyurethane foam constituting the vehicle sound insulation material of this disclosure (hereinafter sometimes referred to as "the polyurethane foam of this disclosure"), the skeleton is stiffened to achieve rigidity of ASKER C hardness 45 or higher. As mentioned above, simply stiffening the skeleton makes it difficult for the foam film to rupture, thus hindering cell interconnection. However, in the polyurethane foam of this disclosure, a connected cell structure is achieved while reducing the cell diameter. Reducing the cell diameter lengthens the sound propagation path, improving sound absorption. Extending the sound propagation path is particularly effective for sound absorption in the longer wavelength (low-frequency) region. Furthermore, by creating a connected cell structure, even with a small cell diameter, the air resistance is not easily increased. Therefore, the polyurethane foam disclosed herein has a vertical incident sound absorption coefficient of 0.30 or higher at a frequency of 800 Hz and a vertical incident sound absorption coefficient of 0.50 or higher at a frequency of 5000 Hz, achieving high sound absorption in both the low-frequency and high-frequency regions.

[0010] In the engine compartment of a vehicle, not only radiated sound from noise sources but also reverberating sound within the space becomes a target for reduction. The polyurethane foam of this disclosure possesses the desired rigidity, thus allowing it to be used alone without the need for support from rigid cover components. In this case, sound absorption properties are achieved on both sides of the polyurethane foam (the side facing the noise source and the opposite side), thereby further enhancing its effectiveness as a sound insulation material. Furthermore, by avoiding the use of rigid cover components, the vehicle sound insulation material of this disclosure can be lightweight, and it can be easily fixed to the target component using methods such as clips.

[0011] (2) In the above configuration, the polyurethane foam may also have a density of 90 kg / m³. 3 Above and 1600kg / m 3 For example, increasing the density of polyurethane foam can reduce the cell diameter, but this reduces the air layer and thus decreases sound absorption. According to this configuration, the cell diameter can be reduced while maintaining a relatively low density, thus minimizing the reduction in sound absorption.

[0012] Invention Effects The vehicle sound insulation material disclosed herein exhibits high sound absorption in both the low-frequency and high-frequency regions. Furthermore, the vehicle sound insulation material of this disclosure enables weight reduction and cost cuts. Attached Figure Description

[0013] Figure 1 This is a graph showing the vertical incident sound absorption coefficients of the polyurethane foams in the examples and comparative examples. Detailed Implementation

[0014] The following describes embodiments of the vehicle sound insulation material disclosed herein. Furthermore, the embodiments are not limited to the following methods and can be implemented in various modifications and variations that can be made by those skilled in the art. In the numerical ranges described in this specification, the individually described upper and lower limits can be arbitrarily combined. Additionally, the upper and lower limits of the numerical ranges can be replaced with the values ​​shown in the embodiments.

[0015] In the vehicle sound insulation material disclosed herein, there are no particular limitations on the composition other than polyurethane foam. The vehicle sound insulation material of this disclosure may consist solely of polyurethane foam, or it may be composed of a combination of polyurethane foam and other components. For example, when the vehicle sound insulation material of this disclosure is specifically embodied as an engine hood, the engine hood may be a single-layer structure of polyurethane foam, or it may be a multi-layer structure having a sound insulation layer made of polyurethane foam and a skin layer covering the sound insulation layer. The skin layer may be formed using resin, elastomer, metal, fiber, etc. Furthermore, the term "vehicle" as used includes not only automobiles, but also aircraft, trams, etc. The polyurethane foam constituting the vehicle sound insulation material of this disclosure will be described below.

[0016] <Physical Properties and Characteristics of Polyurethane Foam> Average cell diameter The polyurethane foam disclosed herein has an average cell diameter of 50 μm or more and 200 μm or less. When the average cell diameter is less than 50 μm, the air resistance becomes too high, thus reducing sound absorption. More preferably, the average cell diameter is 70 μm or more, 100 μm or more, or 120 μm or more. On the other hand, if the average cell diameter is greater than 200 μm, the sound propagation path becomes shorter, particularly reducing sound absorption in the low-frequency region. More preferably, the average cell diameter is 180 μm or less. In this disclosure, the average cell diameter is measured using a cell structure analysis device, "PORE!SCAN," manufactured by Goldluecke Corporation. Specifically, image analysis is performed on a cross-section of the polyurethane foam in the thickness direction (10 mm or more longitudinally and 50 mm or more transversely), and the arithmetic mean of the obtained cell diameters is taken as the average cell diameter.

[0017] [Ventilation resistance] The polyurethane foam disclosed herein has an air resistance of 0.2 kPa·s / m or more and 5 kPa·s / m or less. When the air resistance is less than 0.2 kPa·s / m, the sound propagation path becomes shorter, and the sound absorption in the low-frequency region decreases. More preferably, the air resistance is 0.3 kPa·s / m or more. On the other hand, if the air resistance is greater than 5 kPa·s / m, the sound absorption decreases. More preferably, the air resistance is 4 kPa·s / m or less. In this disclosure, the air resistance is measured using an air resistance testing machine "KES-F8" manufactured by Kato Technology Co., Ltd. Specifically, for a circular plate-shaped sample with a diameter of 40 mm and a thickness of 10 mm, the air resistance is measured at a constant flow rate V[m] at a piston speed of 0.2 cm / s. 3 / (m 2 The pressure difference ΔP[kPa] between the air pressure passing through and atmospheric pressure is used as the ventilation resistance, and the value R[kPa·s / m] calculated by the following formula (I) is used as the ventilation resistance.

[0018] R = ΔP / V···(I) The air resistance of polyurethane foam varies depending on its cell structure. The cell structure can be adjusted by the composition and proportion of the raw materials (foaming polyurethane resin raw materials) of the polyurethane foam, or by compressing the polyurethane foam with rollers or other means after foaming.

[0019] [ASKER C Hardness] The polyurethane foam disclosed herein has an ASKER C hardness of 45 or higher. A hardness less than 45 results in insufficient rigidity. More preferably, the ASKER C hardness is 50 or higher, and even more preferably 60 or higher. On the other hand, if the ASKER C hardness is too high, it becomes difficult to achieve cell connectivity, making it difficult to obtain the desired cell structure. Therefore, the ASKER C hardness is preferably 70 or lower. In this disclosure, the ASKER C hardness is measured using the peak value of an "ASKER Rubber Hardness Tester Type C" manufactured by Polymer Instrument Co., Ltd., based on the spring hardness test type C specified in JIS K7312-1996.

[0020] [density] The density of the polyurethane foam disclosed herein is preferably 90 kg / m³. 3 Above and 1600kg / m 3 The following applies to areas with a density less than 90 kg / m³. 3 Under these conditions, it is difficult to obtain the desired rigidity. A more preferred density is 100 kg / m³. 3 That's all. On the other hand, if the density is greater than 1600 kg / m³ 3 This results in less air layer and reduced sound absorption. A more preferable density is 1000 kg / m³. 3 Below, 500kg / m 3 Below, 160kg / m 3 In this disclosure, density is calculated by dividing the mass of the polyurethane foam of the test object by its volume.

[0021] [Vertical Incident Sound Absorption Coefficient] The polyurethane foam disclosed herein has a vertical incident sound absorption coefficient of 0.30 or higher at a frequency of 800 Hz and 0.50 or higher at a frequency of 5000 Hz. In this disclosure, the vertical incident sound absorption coefficient is measured using a circular plate-shaped sample with a diameter of 30 mm and a thickness of 10 mm, and by the method described in JIS A1405-2:2007. The vertical incident sound absorption coefficient is acceptable to be 0.30 or higher at 800 Hz and 0.50 or higher at 5000 Hz, but is preferably 0.30 or higher in the frequency range between 800 Hz and 5000 Hz, and even more preferably in the high-frequency range exceeding 5000 Hz to 6300 Hz.

[0022] [Flame retardancy] Components located in the engine compartment of a vehicle are also required to be flame-retardant. Therefore, the polyurethane foam disclosed herein preferably has, for example, a flame-retardant level of V-2 according to the UL94 standard. Specifically, if the following vertical burning test according to the UL94 standard is performed and all the judgment criteria (1) to (5) are met, it is judged to be at the V-2 level.

[0023] Vertical combustion test: The flame of the gas burner is brought into contact with the lower end of the vertically positioned specimen for 10 seconds. If combustion stops within 30 seconds, the specimen is brought into contact with the flame for an additional 10 seconds.

[0024] Judgment Criteria: (1) The sample does not burn for more than 30 seconds in either of the two exposures to the flame. (2) The total burning time of the five samples after two exposures to the flame does not exceed 250 seconds. (3) No sample burns to the position of the fixing fixture. (4) There is dripping of burning particles that ignites the cotton placed below the sample. (5) After the second exposure to the flame, the sample remains red-hot for no more than 60 seconds.

[0025] <Manufacturing Methods of Polyurethane Foam> The polyurethane foam disclosed herein can be manufactured by foaming a polyurethane resin raw material composed of isocyanate, polyol, catalyst, foaming agent, etc. Alternatively, the cell structure can be adjusted by compression or other methods after foaming.

[0026] There are no particular limitations on the isocyanate component, as long as it forms a carbamate bond through reaction with the polyol component. For example, it can be appropriately selected from toluene diisocyanate (TDI), phenyl diisocyanate, diphenylmethylene diisocyanate, diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate (NDI), and their derivatives. Examples of derivatives include prepolymers obtained by reacting isocyanates with polyols, modified polyisocyanates, and polymeric MDI (polynuclear) having three or more isocyanate groups and three or more benzene rings per molecule.

[0027] As a polyol component, it can be appropriately selected from polyhydroxy 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, etc.

[0028] Examples of catalysts include amine catalysts such as tetraethylenediamine, triethylenediamine, and dimethylethanolamine, as well as organometallic catalysts such as tin laurate and tin octoate. Examples of foaming agents include water, dichloromethane, Freon, and CO2 gas.

[0029] Polyurethane foam resin raw materials can further include foam stabilizers, plasticizers, crosslinking agents, chain extenders, flame retardants, antistatic agents, viscosity reducers, stabilizers, fillers, and colorants. 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.

[0030] Polyurethane foam resin raw materials can be prepared by adding isocyanate to a premixed polyol, which is formed by premixing components other than isocyanate into a polyol component. In this case, the premixed polyol and isocyanate components can be mechanically stirred using a propeller or the like, or the premixed polyol and isocyanate components can be discharged separately under high pressure using a high-pressure injection machine or the like, causing the two components to collide and mix. The premixed polyol and isocyanate components are preferably formulated with an isocyanate index (equivalent of isocyanate groups / equivalent of active hydrogen groups × 100) of 100 or more and 150 or less, preferably 100 or more and 120 or less.

[0031] Example Next, embodiments will be provided to illustrate this disclosure in more detail.

[0032] Manufacturing of Polyurethane Foam [Example 1] First, 70 parts by weight of polyether polyol (EXCENOL 837, manufactured by AGC Co., Ltd.) and 30 parts by weight of polymer polyol (SANNIX KC-900, manufactured by Sanyo Chemical Industries, Ltd.) were mixed with 1 part by weight of diethanolamine (a crosslinking agent), 3 parts by weight of water (a foaming agent), 0.3 parts by weight of amine catalyst A (DABCO 33LV, manufactured by EVONIK Co., Ltd.), and 0.1 parts by weight of amine catalyst B (Niax Catalyst A-1, manufactured by MOMENTIVE Co., Ltd.) to prepare a premixed polyol. Next, the prepared premixed polyol was mixed with polymeric MDI (LUPRANATE M20S, manufactured by BASF INOAC Polyurethane Co., Ltd.) as an isocyanate component, with an isocyanate index of 100, to prepare a foamed polyurethane resin raw material.

[0033] Then, a wax-based water-based release agent is applied to the mold surface of the molding die, which is pre-adjusted to 58°C. The foamed polyurethane resin raw material is then injected into the cavity of the molding die (a cuboid 500mm long, 600mm wide, and 10mm thick), sealed, and allowed to foam for 5 minutes. Next, the polyurethane foam (10mm thick) is removed from the molding die and passed between a pair of rollers to crush both sides. The rollers are spaced 1mm apart, and the compression rate of the polyurethane foam during crushing is 90%. This produces the polyurethane foam of Example 1.

[0034] [Example 2] In the method for manufacturing polyurethane foam in Example 1, the water content of the foaming agent was increased to 4 parts by mass, and rollers with a spacing of 5 mm were used during compression to achieve a compression rate of 50% for the polyurethane foam. Otherwise, the polyurethane foam of Example 2 was manufactured in the same manner as in Example 1.

[0035] [Comparative Example 1] In the polyurethane foam manufacturing method of Example 1, except that the foam is not crushed after foaming, the polyurethane foam of Comparative Example 1 is manufactured in the same manner as in Example 1.

[0036] [Comparative Example 2] As a comparative example 2, polyurethane foam “CALMFLEX (registered trademark) UGR” manufactured by INOAC CORPORATION was prepared.

[0037] [Comparative Example 3] In the method for manufacturing polyurethane foam in Example 1, except that the amount of water in the foaming agent was increased to 4 parts by mass, the polyurethane foam of Comparative Example 3 was manufactured in the same manner as in Example 1.

[0038] [Comparative Example 4] In the polyurethane foam manufacturing method of Example 1, the water content of the foaming agent was increased to 4 parts by mass, and rollers with a spacing of 5 mm were used during compression to achieve a compression rate of 50% for the polyurethane foam. Otherwise, the polyurethane foam of Comparative Example 4 was manufactured in the same manner as in Example 1. In addition, in the manufacturing of the polyurethane foam of Comparative Example 4, the number of compressions was increased compared to the manufacturing of the polyurethane foam of Example 2, and a thorough interconnection process was performed.

[0039] Evaluation of Polyurethane Foam The average cell diameter, air resistance, ASKER C hardness, density, and vertical incident sound absorption coefficient of the manufactured polyurethane foam were measured to evaluate its rigidity and sound absorption properties.

[0040] [Determination Method] (1) Average bubble diameter The average cell diameter was determined by image analysis of the cross-section (10 mm long and 50 mm wide) of polyurethane foam in the thickness direction using the "PORE!SCAN" cell structure analysis device manufactured by Goldluecke.

[0041] (2) Ventilation resistance The air permeability resistance of polyurethane foam was determined using the "KES-F8" air permeability testing machine manufactured by Kato Technology Co., Ltd. In the test, a circular plate-shaped sample with a diameter of 40 mm and a thickness of 10 mm, cut from the manufactured polyurethane foam, was used, and a constant flow rate of 0.4 cc / (cm³) was applied at a piston speed of 0.2 cm / s. 2 ·s)(=4×10 -3 m 3 / (m 2 The air passes through.

[0042] (3) ASKER C hardness The ASKER C hardness of polyurethane foam was measured using the "ASKER Rubber Hardness Tester Type C" manufactured by Polymer Instrument Co., Ltd., and the peak value was read.

[0043] (4) Density Density is calculated by dividing the mass of polyurethane foam by its volume.

[0044] (5) Vertical incident sound absorption coefficient Using circular plates with a diameter of 30 mm and a thickness of 10 mm cut from the manufactured polyurethane foam, the vertical incident sound absorption coefficient was determined according to the method described in JISA 1405-2:2007. Then, a vertical incident sound absorption coefficient of 0.30 or higher at a frequency of 800 Hz was evaluated as good sound absorption (indicated by the ○ symbol in Table 1), and a coefficient less than 0.30 was evaluated as poor sound absorption (indicated by the × symbol in the table). Similarly, a vertical incident sound absorption coefficient of 0.50 or higher at a frequency of 5000 Hz was evaluated as good sound absorption (indicated by the ○ symbol in Table 1), and a coefficient less than 0.50 was evaluated as poor sound absorption (indicated by the × symbol in the table).

[0045] [Measurement Results] Table 1 shows the physical properties and characteristics of the polyurethane foams of the examples and comparative examples. Figure 1 A graph showing the vertical incident sound absorption coefficient of each polyurethane foam relative to frequency is presented. Figure 1 In the diagram, black dots represent points with an absorption coefficient of 0.30 relative to 800Hz and points with an absorption coefficient of 0.50 relative to 5000Hz.

[0046] [Table 1]

[0047] As shown in Table 1, the polyurethane foams of Examples 1 and 2 meet the conditions of an average cell diameter of 50 μm or more and 200 μm or less, an air resistance of 0.2 kPa·s / m or more and 5 kPa·s / m or less, and an ASKER C hardness of 45 or more, exhibiting the desired rigidity. Furthermore, the density is also 90 kg / m³. 3 Above and 1600kg / m 3 Furthermore, in the polyurethane foam of Example 1, the vertical incident sound absorption coefficient at 800 Hz was 0.32, and at 5000 Hz it was 0.52. In the polyurethane foam of Example 2, the vertical incident sound absorption coefficient at 800 Hz was 0.31, and at 5000 Hz it was 0.52, confirming high sound absorption in both the low-frequency and high-frequency regions. Additionally, as... Figure 1 As shown, the vertical incident sound absorption coefficient is above 0.30 in the entire region with frequencies above 800Hz and below 5000Hz.

[0048] In contrast, in the polyurethane foam of Comparative Example 1, the air resistance was too high, exceeding 25 kPa·s / m, resulting in a low vertical incident sound absorption coefficient at both 800 Hz and 5000 Hz, indicating poor sound absorption. In the polyurethane foam of Comparative Example 2, the air resistance was too low, at 0 kPa·s / m, indicating excessive softness and an ASKER C hardness of 0. The vertical incident sound absorption coefficient was above 0.50 at 5000 Hz, but less than 0.30 at 800 Hz, indicating poor sound absorption in the low-frequency region. In the polyurethane foam of Comparative Example 3, the air resistance was less than 0.2 kPa·s / m, and the vertical incident sound absorption coefficient was above 0.50 at 5000 Hz, but less than 0.30 at 800 Hz, indicating poor sound absorption in the low-frequency region. In the polyurethane foam of Comparative Example 4, the air resistance was greater than 5 kPa·s / m, and the vertical incident sound absorption coefficient decreased at frequencies of 800 Hz and 5000 Hz, indicating poor sound absorption.

[0049] Industrial applicability The vehicle sound insulation material disclosed herein is suitable not only as a cover for an eAxle (an electric drive module that integrates an electric motor, a transmission drive axle, and an inverter), an engine cover, a timing chain cover, a side cover, an oil pan cover, an inverter cover, a compressor cover, a front bulkhead insulator, a floor insulator, a rear storage plate, wheel cover pads, and a bottom cover, but also as a sound insulation material disposed around a transmission, etc.

Claims

1. A sound insulation material for vehicles, comprising polyurethane foam, wherein, The polyurethane foam has an average cell diameter of ≥50μm and ≤200μm, an air resistance of ≥0.2kPa·s / m and ≤5kPa·s / m, and an ASKER C hardness of ≥45. When the vertical incident sound absorption coefficient of the polyurethane foam was measured using a circular plate sample with a diameter of 30 mm and a thickness of 10 mm, the sound absorption coefficient at a frequency of 800 Hz was greater than 0.30, and the sound absorption coefficient at a frequency of 5000 Hz was greater than 0.

50.

2. The sound insulation material for vehicles according to claim 1, wherein, The density of the polyurethane foam is 90 kg / m³. 3 Above and 1600kg / m 3 the following.

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