JP2014028612A - Sound absorption material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance of a sound absorption material in which chips 12 are used.SOLUTION: A sound absorption material is provided with a chip material layer 21 which comprises many chips 12, and an air-permeable skin layer 22 covering at least one face of the chip material layer 21. A flow resistance value of the chip material layer 21 is 1×10Ns/mor more and 1×10s/mor less, and a flow resistance value of the skin layer 22 is in the range of 10Ns/morder from 10Ns/morder.

Description

  The present invention relates to a sound absorbing material used for a vehicle or the like.

  Vehicles and other vehicles and buildings are provided with a sound absorbing material in order to obtain a quiet interior. For example, an inner fender may be provided in a wheel house of a vehicle (automobile) fender, and a sound absorbing material may be attached to the inner fender as a countermeasure against road noise. In addition, sound absorbing materials are provided in various parts of the vehicle such as the dash panel and the hood panel. Patent Document 1 describes that a sound absorbing material made of a nonwoven fabric, urethane sponge, or the like is attached to an inner fender of a vehicle.

  There is also known a sound absorbing material formed by laminating two or more kinds of different materials. For example, Patent Document 2 and Patent Document 3 describe a sound absorbing material for an inner fender in which a water-resistant film is laminated on a sound absorbing base material such as a nonwoven fabric.

  Patent Document 4 describes that a sound absorbing material formed by filling a breathable container with a chip-like foam is used for a vehicle or the like. Examples of the breathable container include a bag made of a breathable sheet such as a non-woven fabric. Employing an olefin-based elastomer or the like as the chip-like foam, setting the size of the chip-like foam to 2 to 20 mm, It is also described that the chip-like foam is compressed and filled into a breathable container.

  Patent Document 5 describes that a sound-absorbing material obtained by enclosing pulverized foam particles obtained by pulverizing a styrene resin foam in a breathable or non-breathable bag-like material is used for a vehicle or the like.

Patent Document 6 discloses a dash silencer to be mounted on a dash panel of a vehicle, a non-woven fabric having a flow resistance value of 200 Nsm ⁻³ or more and 1000 Nsm ⁻³ or less, a felt having a thickness of 5 to 50 mm and an area density of 200 to 3000 g / m ² . It is described that it is made into the laminated structure.

JP 2010-006312 A Japanese Patent No. 3675359 JP 2011-240821 A JP 2005-316353 A JP 2003-150169 A JP 2002-264736 A

As described above, a sound absorbing material having a laminated structure is already known and put to practical use, but further improvement in sound absorbing performance is desired. For example, felt is widely used as a sound absorbing material, but even if a nonwoven fabric is laminated on the felt, the sound absorbing performance is hardly changed. 11 and the sound absorbing material flow resistance is formed of only the felt 10 ^{4 Ns} / m 4 orders, a normal incidence sound absorption coefficient of the sound absorbing material flow resistance by laminating 10 6 ^Ns / m ⁴ order of nonwoven this felt It is a seen graph. According to the figure, it can be seen that even if a non-woven fabric is laminated on the felt, the frequency at which the sound absorption coefficient peaks is slightly shifted to the low frequency side, and an increase in the sound absorption coefficient can hardly be expected.

  Of course, the thicker the sound absorbing material, the higher the sound absorbing performance. However, in general, the thickness is often limited, for example, when the sound absorbing material is provided in a narrow gap between the inner fender and the fender.

  Therefore, the present invention aims to further improve the sound absorbing performance without excessively increasing the thickness of the sound absorbing material. In particular, the present invention aims to improve the performance of a sound absorbing material using a chip material such as a chip-like foamed elastic body.

  In order to solve the above-mentioned problems, the present inventor conducted various experiments and studies on the performance of the sound absorbing material using the chip material. When a film layer is provided on the chip material layer, the sound absorption depends on the flow resistance value of the film layer. The present invention was completed by finding that the performance changed greatly.

The sound absorbing material presented here includes a chip material layer containing a large number of chip materials, and a breathable coating layer covering at least one surface of the chip material layer,
The chip material layer has a flow resistance value in the thickness direction of the order of 10 ³ Ns / m ⁴ (1 × 10 ³ Ns / m ⁴ or more and less than 1 × 10 ⁴ s / m ⁴ ),
The film layer has a flow resistance value in the thickness direction of the order of 10 ⁵ Ns / m ⁴ to 10 ⁸ Ns / m ⁴ (1 × 10 ⁵ Ns / m ⁴ or more and less than 1 × 10 ⁹ Ns / m ^4. ).

  That is, for example, the sound absorbing material described in Patent Document 4 is also formed by filling a chip-shaped foam into a bag body made of a breathable sheet such as a non-woven fabric, and thus has a chip material layer and a coating layer. You might say. However, this Patent Document 4 only discloses the combination of a breathable sheet and a chip-like foam, and the flow resistance value of each of the breathable sheet and the chip-like foam is stepped down to what should be. Not. Patent document 6 also specifies only the flow resistance value of a nonwoven fabric in the combination of the same kind of material of a nonwoven fabric and felt.

On the other hand, according to the present invention, in the case where the flow resistance value of the chip material layer is on the order of 10 ³ Ns / m ⁴ , the flow resistance value of the coating layer is changed from 10 ⁵ Ns / m ⁴ order to 10 ⁸ Ns / m. by set to a range of m ⁴ orders, as compared to the sound absorbing material consisting of only the chip material layer, an unexpected effect that the peak value of the sound absorption rate becomes remarkably high and the frequency band which exhibits a sound absorbing effect spreads can get. Although this will be clarified in the sound absorption characteristic data described later, the reason why such an effect is obtained is not necessarily clear, but is considered as follows.

  That is, in the chip material layer, viscosity loss due to the movement of air around each chip material due to the incidence of sound, or friction loss between air and the chip material, friction loss between the chip materials, and further of the chip material itself It is thought that the sound absorption effect is exhibited by internal loss due to vibration. On the other hand, in the air-permeable film layer, not only has the sound absorption effect due to the above-mentioned viscosity and friction, but the internal loss due to the film vibration of the film layer when the sound is incident occupies a relatively large weight for sound absorption. Conceivable. In that case, the sound absorption rate by the coating layer becomes high at the resonance frequency at which the amplitude of the membrane vibration becomes maximum, but this resonance frequency changes according to the flow resistance value of the coating layer.

Thus, in the present invention, the flow resistance value of the coating layer is set in the range of 10 ⁵ Ns / m ⁴ order to 10 ⁸ Ns / m ⁴ order as described above. The resonance frequency of the coating layer appears in a frequency range that is relatively close to the frequency that becomes. In addition, since the coating layer having the above flow resistance value is allowed to transmit sound waves to some extent, sound absorption in the chip material layer can also be achieved. Therefore, it is considered that the sound absorption rate by the resonance of the coating layer is added to the sound absorption effect by the chip material layer, and the sound absorption rate as a whole of the sound absorption material is remarkably increased. The frequency at which the sound absorption coefficient reaches a peak is different between the chip material layer and the film layer. In the film layer having a high flow resistance value, a resonance frequency appears on the lower frequency side than the chip material layer. Therefore, it is considered that the sound absorption coefficient is increased in a wide frequency range.

  Further, since the chip material layer contains a large number of chip materials, the thickness can be changed by compression. Therefore, the sound absorbing material can be compressed and installed in a required installation location according to the space. Here, since the film layer has air permeability, there is no problem in compressing the sound absorbing material even when the surface of the chip material layer opposite to the film layer is covered with a non-air-permeable film layer.

More preferably, the flow resistance value of the coating layer is set in the range of 10 ⁵ s / m ⁴ to 10 ⁷ Ns / m ⁴ , and further the flow resistance value is set to 10 ⁶ s / m. It is preferable to set in the range of ⁴ orders to 10 ⁷ Ns / m ⁴ orders.

  The chip material can be short, spherical, irregularly crushed, flaky, etc., and the shape thereof is not limited, and the material such as rubber, plastic, wood, paper, etc. is not limited. And it does not matter whether they are foamed or not. The flakes may have a rounded shape, a shape that is distorted so as to have irregularities, or a shape in which the peripheral edge is rolled up.

  It is preferable that the chip material layer has elasticity or compression recovery, but it is not always necessary that the individual chip material itself has elasticity or compression recovery. For example, the chip material layer may have elasticity or compression restoring property by curving the rounded flaky chip material elastically.

It is preferable that the dynamic longitudinal elastic modulus of the above-mentioned chip material layer is 1 × 10 ⁵ N / m ² or more and 1 × 10 ⁷ N / m ² or less in repeated operations of compression / compression release from 100 Hz to 1000 Hz. More preferably, it is 4 × 10 ⁵ N / m ² or more and 5 × 10 ⁶ N / m ² or less. Further, the loss coefficient from 100 Hz to 1000 Hz is preferably 0.05 or more and 0.5 or less, and more preferably 0.1 or more and 0.4 or less.

The density (true specific gravity) of the chip material is about 0.01 g / cm ³ or more and 1.5 g / cm ³ or less, and further about 0.03 g / cm ³ or more and 0.5 g / cm ³ or less. preferable. In particular, the bulk density of the chip material (apparent density when the chip material is filled in a container in a free state (non-compressed state)) is about 0.01 g / cm ³ or more and 0.99 g / cm ³ or less. It is preferable that it is about 0.03 g / cm ³ or more and 0.5 g / cm ³ or less.

  Preferred as the above-mentioned chip material is a chip-like foam having an irregularly crushed shape (not a regular shape such as a dice, sphere, strip, rectangular sheet, etc., but an irregular shape (an irregular shape) and irregular sizes). It is an elastic body (hereinafter referred to as “foamed elastic chip”). The average particle size is preferably about 0.5 mm to 5 mm, for example, and the particle size range is preferably about 0.1 mm to 10 mm, for example.

  As the foamed elastic body chip, for example, an olefin-based EPDM (ethylene-propylene-diene copolymer) rubber foam can be preferably used, but NR (natural rubber), IR (isoprene rubber), SBR ( Styrene-butadiene rubber), CR (chloroprene rubber), thermoplastic elastomer (olefin-based or styrene-based thermoplastic elastomer), soft polyvinyl chloride, or other foams made of other rubber or other elastic materials may be used. Good. However, from the viewpoint of enhancing sound absorption, the foamed elastic chip has foam cells (sponge foaming eyes) exposed on the surface without at least a part of the foam being covered with a skin layer. Is preferred. In other words, it is desirable that the uneven surface of the foam cell is exposed.

  The chip material may be a foamed chip of a thermoplastic resin (plastic) that is not an elastic material. The thermoplastic resin may be any material as long as it is used for general industrial use, such as olefin, styrene, amide, epoxy, urethane, and polyester. Polypropylene (PP), polyethylene (PE), and polymers thereof are preferable.

  The chip material may be a non-foamed chip. This is also an irregularly crushed shape (not a regular shape such as a dice, sphere, strip or rectangular sheet, but an irregular shape (an irregular shape) and irregular sizes), for example, a thick or thin sheet The surface may be crushed so that the surface becomes uneven, and a protruding part that is partially twisted on the surface may be generated. The average particle size is preferably about 0.5 mm to 10 mm, for example, excluding the twisted portion protruding from the chip material body, and the particle size range is preferably about 0.1 mm to 20 mm, for example. As a material of such a chip material, an elastic material or an inelastic material exemplified in the above-described foamed elastic chip or foamed chip is preferable.

In the chip material layer, a foamed elastic chip, a foamed chip, or a non-foamed chip may be constituted alone, or two or more of these may be mixed. The chip material is a main material (for example, 80% or more in volume ratio), and other sound absorbing materials or fillers such as fiber materials and inorganic material powders (silica, mica, etc.). Also good. Further, the thickness of the chip material layer is determined by the size of the space in which the sound absorbing material is installed, but if the thickness is 5 mm or more and 100 mm or less, the desired sound absorbing performance can be obtained. Of course, in order to further improve the sound absorption performance, the thickness can be increased beyond 100 mm. The surface density of the entire sound absorbing material may be about 1 kg / m ² or more and 4 kg / m ² or less.

As the coating layer, a non-woven fabric or a woven fabric made of natural fibers or chemical fibers can be preferably used. However, the chemical fibers may be organic fibers or inorganic fibers as long as they have a flow resistance value of the order. Also, paper may be used, and the material is not particularly limited. For example, a resin sheet having no air permeability may be provided with a large number of air holes. The thickness of the coating layer is preferably about 0.01 mm or more and 3 mm or less, and more preferably 1.0 mm or less. Further, the surface density of the coating layer is, for example, preferably 80 g / m ² or more and 500 g / m ² or less, and more preferably 150 g / m ² or less. Here, as for what provided many air holes in the resin-made sheet | seat which does not have air permeability, the material is polyethylene and the thickness of a film layer is 0.01 mm or more and 1 mm or less, Preferably it is 0.5 mm or less. Conceivable.

  The sound-absorbing material according to the present invention can be obtained, for example, by enclosing a large number of chip materials in a flat bag (a flat bag having few irregularities and flat). In this case, one side of the flat bag forms the coating layer, and the multiple chip materials enclosed in the flat bag form the chip material layer. A flat bag can be obtained, for example, by superposing two sheet materials such as non-woven fabrics or folding one sheet material and joining the overlapped peripheral portions. The overlapped peripheral edge portion only needs to be joined to such an extent that the contents such as the chip material do not come out, and the joining is not limited to heat fusion, and an appropriate method such as adhesion and stitching is adopted. be able to.

As described above, according to the present invention, the chip material layer having a flow resistance value of the order of 10 ³ Ns / m ⁴ is provided, and the flow resistance value of the coating layer covering at least one surface of the chip material layer is 10 ^5. By setting the range from Ns / m ⁴ order to 10 ⁸ Ns / m ⁴ order, the sound absorbing performance of the sound absorbing material using the chip material can be greatly improved without excessively increasing the thickness of the sound absorbing material. In addition, there is an effect that the frequency range in which the sound absorbing effect is exhibited is widened.

It is a perspective view which shows an example of the vehicle using the sound-absorbing material which concerns on this invention. It is a perspective view which shows an inner fender and a sound-absorbing material. It is a perspective view which notches and shows a part of said sound-absorbing material. It is a perspective view which shows the example of manufacture of the said sound-absorbing material. It is sectional drawing (enlarged drawing of the dashed-dotted circle A part of FIG. 3) of the said sound-absorbing material. It is a graph which shows the dynamic longitudinal elastic modulus of a chip material layer. It is a graph which shows the loss coefficient of a chip material layer. It is a graph which shows the sound absorption characteristic of a sound-absorbing material sample. It is a graph which shows the relationship between the compression rate of a chip material layer, and a flow resistance value. It is a graph which shows the influence which the compressibility of a chip material layer has on the sound absorption characteristic of a sound-absorbing material. It is a graph which shows the sound absorption characteristic of the conventional sound-absorbing material.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its use.

<Example of vehicle using sound absorbing material>
FIG. 1 shows a vehicle 1 as an example using a sound absorbing material according to the present invention. In the figure, reference numeral 2 denotes a front fender, and an inner fender 5 shown in FIG. 2 is provided as a lining inside the tire house 3 (on the tire 4 side). The inner fender 5 prevents scratches, rust, noise, and the like inside the front fender 2 due to pebbles and water that the tire 4 jumps up. As shown in FIG. 2, a sound absorbing material 6 is mounted on the upper surface side (the surface opposite to the tire 4) of the inner fender 5 as a countermeasure against road noise and other noises. The sound absorbing material 6 is provided with a water drain hole 7. The sound absorbing material 6 is also attached to other parts of the vehicle body such as the inner fender 8 and the dash panel 9 on the rear fender side, the upper surfaces of the under floor covers 10a to 10c, the side door 25, the roof 26, etc., in order to provide quietness in the passenger compartment. can do.

  Further, the drain hole 7 may be an attachment hole used for attaching to the inner fender 5. Further, as will be described later, the sound-absorbing material 6 has a joining portion at the peripheral portion, and this joining portion is bonded partially or over the entire circumference (adhesion with an adhesive or a material of the joining portion) or a stapler, a bolt, or the like. It can fix to the inner fender 5 with a fastener.

<About sound absorbing material>
As shown in FIG. 3, the sound absorbing material 6 according to this embodiment is configured by enclosing a chip material 12 in a flat bag 11. The flat bag 11 is closed over the entire circumference. This will be specifically described below.

  The flat bag 11 is formed by joining the peripheral edges of two nonwoven fabrics 13 and 14 having air permeability over the entire circumference. Although it does not necessarily limit, if an example is described, the nonwoven fabrics 13 and 14 will consist of a chemical fiber of polyethylene (PE) and polyethylene terephthalate (PET). For example, heat fusion is employed for joining the peripheral portions of the nonwoven fabrics 13 and 14. The individual chip materials 12 are non-adhered to each other and can be displaced. The chip material 12 is not bonded to the flat bag 11.

  FIG. 4 shows the flat bag material 16 before enclosing the chip material 12. The flat bag material 16 has a body portion 17 and a tip insertion portion 18 connected by a neck portion 19, and a tip insertion portion 20 is provided in the tip insertion portion 18. The chip material 12 is filled into the body portion 17 of the flat bag material 16 from the insertion port 20 of the chip insertion portion 18. After filling, the neck portion 19 of the flat bag material 16 is closed by heat fusion. The sound absorbing material 6 is obtained by separating the chip insertion portion 18 from the body portion 17 filled with the chip material 12. The body portion 17 of the flat bag material 16 becomes the flat bag 11.

  As shown in FIG. 5, in the sound absorbing material 6, a large number of chip materials 12 interposed between the nonwoven fabrics 13 and 14 of the flat bag 11 form a chip material layer 21. In this example, sound is incident from the bottom to the top of the figure, and the nonwoven fabric 13 forms a surface on the chip material layer 21 on which sound to be absorbed is incident, that is, an incident-side film layer 22. ing. The non-woven fabric 14 covering the surface of the chip material layer 21 opposite to the surface on which the target sound is incident forms the back-side coating layer 23. The incident side coating layer 22 and the back side coating layer 23 are not bonded to the chip material layer 21. The sound absorbing material 6 is stacked on the vehicle body so that the incident-side film layer 22 is in contact with the upper surface of the inner fender 5 as shown in FIG. In FIG. 5, the inner fender 5 is indicated by a two-dot chain line, and the incident side coating layer 22 and the inner fender 5 are not bonded. A gap may be formed between the back-side coating layer 23 and the tire house 3 of the front fender 2. As described above, the joint portion of the peripheral edge portion of the sound absorbing material 6 is fixed to the inner fender 5. In the present embodiment, the joining portion of the peripheral portion of the sound absorbing material 6 is partially fixed to the inner fender 5 by heat fusion.

In the sound absorbing material 6 of the present embodiment, the flow resistance value in the thickness direction of the chip material layer 21 is on the order of 10 ³ Ns / m ⁴ , and the flow in the thickness direction of each of the incident side coating layer 22 and the back side coating layer 23. Resistance values range from 10 ⁵ Ns / m ⁴ order to 10 ⁸ Ns / m ⁴ order. When the chip material 12 is a foamed elastic chip, the average particle diameter is 0.5 mm or more and 5 mm or less (in the individual particles, the maximum diameter is distributed to about 0.1 mm to 10 mm), and the foam density is It is 0.01 g / cm ³ or more and 0.99 g / cm ³ or less. The thickness of the chip material layer 21 is 5 mm or more and 100 mm or less (it is possible to increase the thickness beyond 100 mm). The incident side coating layer 22 and the back side coating layer 23 are both 0.2 mm or more and 3 mm or less in thickness.

<Dynamic longitudinal elastic modulus and loss factor of chip material layer>
As a chip material, an elastic foam chip obtained by pulverizing an end material of a sound insulating sheet made of an EPDM rubber foam (sponge material) into a chip shape, a flaky PE chip obtained by pulverizing a polyethylene sheet, and Prepared. An uncompressed chip material layer in which only foamed elastic chips are stacked to a thickness of 40 mm, an uncompressed chip material layer in which only PE chips are stacked to a thickness of 40 mm, and a foamed elastic chip and a PE chip The dynamic longitudinal elastic modulus and loss factor of each uncompressed chip material layer obtained by stacking mixed chips mixed at a mass ratio of 1: 1 to a thickness of 40 mm were measured.

  For the measurement, a dynamic longitudinal elastic modulus was measured by a resonance method using a vibrator that repeatedly operated in the thickness direction. The loss factor was calculated by the half-width method from the resonance point. The results are shown in FIGS.

As shown in FIG. 6, the dynamic longitudinal elastic modulus of the chip material layer at 100 Hz to 1000 Hz is 1 × 10 ⁵ N / m ² or more and 1 × 10 ⁷ for all of the foamed elastic chip, the PE chip, and the mixed chip. N / m ² or less, and further 4 × 10 ⁵ N / m ² or more and 5 × 10 ⁶ N / m ² or less.

  As shown in FIG. 7, the loss factor of the chip material layer at 100 Hz to 1000 Hz is 0.05 or more and 0.5 or less for all of the foamed elastic chip, the PE chip, and the mixed chip, and further 0.1 It is 0.4 or less.

<Characteristic evaluation 1 of sound absorbing material>
-Sample-
A sound-absorbing material sample A to D having a two-layer structure composed of a chip material layer 21 and an incident-side film layer 22 and a sound-absorbing material sample E composed only of the chip material layer 21 were produced. Samples A to D have different flow resistance values of the incident-side coating layer 22 from each other. The back side coating layer 23 was not installed.

As the chip material constituting the chip material layer 21 of each of the samples A to E, the above-described foamed elastic chip (chip of EPDM rubber foam (sponge material)) was employed. The foamed elastic chip has an average particle size of about 2 mm and a foam density of about 0.3 g / cm ³ . Further, this chip material layer 21 exhibits the characteristics in the preferable ranges of the dynamic longitudinal elastic modulus and the loss coefficient described above, the thickness is 45 mm, the surface density is 2.5 kg / m ² , and the flow resistance value in the thickness direction. Is on the order of 10 ³ Ns / m ⁴ . This flow resistance value was measured in a non-compressed state in which foamed elastic chips were stacked to a thickness of 45 mm. The flow resistance value in the present invention is measured in accordance with the ISO 9053 DC method.

As shown in Table 1, the incident side coating layers 22 of Samples A to C were formed of nonwoven fabrics having different flow resistance values. The incident side coating layer 22 of Sample D was formed of a non-breathable polyethylene sheet having a thickness of 0.08 mm and a flow resistance value of 1 × 10 ⁹ Ns / m ⁴ or more. In the samples A to C, the incident-side coating layer 22 has a thickness of 0.5 mm and an areal density of about 100 g / m ² . Here, in this document, non-ventilation is defined as a flow resistance value of 1 × 10 ⁹ Ns / m ⁴ or more.

-Characterization-
The normal incident sound absorption coefficient in the uncompressed state of each of the samples A to E was measured according to JIS A1405-2. The results are shown in FIG. In addition, the numerical value attached | subjected to the sample symbol of the figure represents the flow resistance value (unit; Ns / m < ⁴ >) of the incident side membrane | film | coat layer.

Sample E consisting only of the chip material layer 21 exhibits sound absorption characteristics having a sound absorption coefficient peak near 1250 Hz. On the other hand, sample A using a nonwoven fabric having a flow resistance value of 4.1 × 10 ⁵ Ns / m ⁴ for the incident side coating layer 22 has a lower sound absorption coefficient peak position than sample E without the incident side coating layer. Slightly shifted to the frequency side, the sound absorption coefficient is high in a wide frequency range from 200 Hz to 2000 Hz. In sample B using a nonwoven fabric having a flow resistance value of 2.8 × 10 ⁶ Ns / m ⁴ , the sound absorption rate near 2000 Hz is slightly lowered, but the sound absorption peak position is further shifted to the lower frequency side, and the sound absorption is reduced. The rate is higher than that of sample A in a wide frequency range from 200 Hz to 1800 Hz.

In the case of Sample C using a nonwoven fabric having a flow resistance value of 4.2 × 10 ⁸ Ns / m ⁴ , the peak value of the sound absorption coefficient is high, but the shift amount of the peak position to the low frequency side is large, The sound absorption coefficient in the vicinity of 1200 Hz to 1500 Hz is low. However, the decrease in the sound absorption coefficient in the vicinity of 1200 Hz to 1500 Hz is not so large, and as a whole, it can be said that a high sound absorption coefficient is obtained in a wide frequency range.

  In sample D using a non-breathable polyethylene sheet for the incident-side film layer 22, the amount of the sound absorption peak shifts to a low frequency side, and the sound absorption coefficient drops significantly in the frequency range of 800 Hz or higher. ing.

From the comparison between the sound absorption characteristics of sample B and the sound absorption characteristics of sample C in FIG. 8, even when the flow resistance value of the incident-side coating layer 22 is set to the order of 10 ⁷ Ns / m ⁴ , the sound absorption coefficient is high in a wide frequency range. Can understand.

<Characteristic evaluation 2 of sound absorbing material>
-Sample-
A sound-absorbing material sample F having a three-layer structure including a chip material layer 21, an incident-side coating layer 22, and a back-side coating layer 23 was produced. For the chip material layer 21, the same foamed elastic chip (EPDM rubber foam (sponge material) chip) as in the previous case (characteristic evaluation 1) was employed. The chip material layer 21 has a thickness of 40 mm, an areal density of 2.0 kg / m ² , and a flow resistance value in the thickness direction in an uncompressed state is 1 × 10 ³ Ns / m ⁴ . The incident-side coating layer 22 and the back-side coating layer 23 are non-woven fabrics having a thickness of 0.5 mm with a flow resistance value of 2.8 × 10 ⁶ Ns / m ⁴ , similar to the incident-side coating layer 22 of the previous sample B. It was adopted.

-Characterization-
The flow resistance value in the thickness direction in each compressed state in which the chip material layer 21 was compressed by 10% to 50% in 10% increments was measured. The results are shown in FIG. The flow resistance value increases as the compression ratio increases, but it is 9 × 10 ³ Ns / m ⁴ even at 50% compression, and is on the order of 10 ³ Ns / m ⁴ .

  Next, with respect to the sound absorbing material sample F having the three-layer structure, the normal incident sound absorbing rate in the non-compressed state and the normal incident sound absorbing rate in each compressed state in which the chip material layer 21 is compressed by 10% to 50% in 10% increments. Were measured by the same method as in the previous characteristic evaluation 1. The results are shown in FIG.

  8 and 10, the sound absorption coefficient of the sample F in the uncompressed state is higher than that of the previous sample B in the range of 500 Hz to 2000 Hz. This is recognized as a result of the difference in the surface density of the chip material layer 21 and the presence / absence of the back side coating layer 23.

  Thus, according to FIG. 10, as the compression rate of the chip material layer 21 increases (the flow resistance value increases), there is a tendency that the shift of the peak position of the sound absorption rate toward the high frequency side increases. However, the amount of decrease in the sound absorption coefficient on the low frequency side due to the shift is small, and high sound absorption performance in a wide frequency range is the same as in the uncompressed state.

That is, if the flow resistance value of the chip material layer 21 is on the order of 10 ³ Ns / m ⁴ , even if the flow resistance value increases within the range of the order, the peak position of the sound absorption coefficient is slightly shifted toward the high frequency side. It can be said that high sound absorption performance can be obtained in a wide frequency range.

In the sound absorbing material characteristic evaluation 1 and the sound absorbing material characteristic evaluation 2, the sample of the chip material is a foamed elastic chip, but the material of the chip material does not have to be a foamed elastic body. The longitudinal elastic modulus is 1 × 10 ⁵ N / m ² or more and 1 × 10 ⁷ N / m ² or less, and further 4 × 10 ⁵ N / m ² or more and 5 × 10 ⁶ N / m ² or less, and the loss coefficient is Either a PE chip or a mixed chip of foamed elastic chip and PE chip (a mass ratio of 1: 1) of 0.05 to 0.5 and 0.1 to 0.4 is used. However, it was confirmed that the same result as the result of the characteristic evaluation was obtained. Moreover, as long as the characteristics required for the chip material layer described in this specification are satisfied, the chip material layer is not limited to the above-described material (polyethylene or foamed elastic body), and may be composed of various materials and mixtures thereof.

<Others>
The back side film layer 23 is not necessarily provided, but when the back side film layer 23 is provided, it may be formed of a non-breathable material such as a polyethylene sheet. Thereby, the back surface side film layer 23 exhibits a sound insulation effect, and the soundproofing property by the sound absorbing material is enhanced. Further, since the back-side film layer 23 exhibits a waterproof effect and prevents water from penetrating into the chip material layer 21, it is advantageous for maintaining the sound absorbing performance and improving the durability of the sound absorbing material. A sound-absorbing material suitable for use in areas that are susceptible to water, such as fenders, can be obtained.

  In the above-described embodiment, an example in which the sound absorbing material according to the present invention is used by being attached to an inner fender or the like of a vehicle has been described. However, the present invention is not limited to this and can be used for other parts such as a dash panel of an automobile. The sound absorbing material of the present invention can be used not only for automobiles but also for other vehicles such as trains and airplanes, and for soundproofing buildings and the like.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Front fender 5 Inner fender 6 Sound absorbing material 11 Flat bag 12 Chip material 21 Chip material layer 22 Incident side coating layer 23 Back side coating layer

Claims (7)

A chip material layer containing a large number of chip materials;
A breathable coating layer covering at least one surface of the chip material layer,
The chip material layer has a flow resistance value in the thickness direction of the order of 10 ³ Ns / m ⁴ ,
The film layer has a flow resistance value in the thickness direction in the range of 10 ⁵ Ns / m ⁴ to 10 ⁸ Ns / m ⁴ . In claim 1,
The chip material layer has a dynamic longitudinal elastic modulus at 100 Hz to 1000 Hz of 1 × 10 ⁵ N / m ² or more and 1 × 10 ⁷ N / m ² or less, and a loss coefficient of 0.05 or more and 0.5 or less. Sound-absorbing material characterized by In claim 1 or claim 2,
The chip material has a bulk density (apparent density when the chip material is filled in a container in a free state (non-compressed state)) of 0.01 g / cm ³ or more and 0.99 g / cm ³ or less, preferably 0. sound absorbing material, characterized in that at .03g / cm ³ or more 0.5 g / cm ³ or less. In any one of Claim 1 thru | or 3,
The chip material layer includes a chip made of a foam of an olefin-based elastic material, a chip made of a foam of an olefin-based inelastic material, a chip made of a non-foamed material of an olefin-based elastic material, and a non-foamed material of an olefin-based inelastic material. A sound-absorbing material comprising one kind selected from a chip made of a body, or a mixture of two or more kinds. In any one of Claims 1 thru | or 4,
The sound absorbing material, wherein the chip material is made of EPDM rubber or polyethylene. In any one of Claims 1 thru | or 5,
The sound absorbing material, wherein the coating layer is made of a nonwoven fabric. In any one of Claims 1 thru | or 6,
A lot of chip materials are enclosed in a flat bag,
A sound-absorbing material, wherein one side of the flat bag forms the film layer, and the plurality of chip materials enclosed in the flat bag form the chip material layer.

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