JP2020106625A - Sound absorption material - Google Patents

Abstract

To provide a sound absorption material which can effectively improve sound absorption performance in a high frequency band of the sound absorption material and is excellent in the sound absorption performance.SOLUTION: The sound absorption material comprises a structure in which a first porous layer, a second porous layer, a third porous layer and a fourth porous layer are laminated in this order. The ventilation resistance per unit thickness of the second porous layer and the fourth porous layer is smaller than the ventilation resistance per unit thickness of the first porous layer, and the ventilation resistance per unit thickness of the first porous layer is smaller than the ventilation resistance per unit thickness of the third porous layer. The sound absorption material comprises the structure in which air permeability of the first porous layer and the third porous layer is 1 cm3/cm2/s or more. Thus, it is found that the sound absorption material excellent in sound absorption performance in a high frequency band (4000 Hz or more, for example) is achieved.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sound absorbing material.

Nowadays, as the living level is improved, quietness is required, for example, in a car room or a living room. Therefore, for the purpose of suppressing the generated noise, for example, a sound absorbing material is installed around the engine of a car, inside the car, in a living room, and in home appliances (for example, inside a vacuum cleaner and a printer).

As a sound absorbing material that can achieve such an object, for example, Japanese Patent Laid-Open No. 8-152890 (Patent Document 1) discloses a laminated structure having a four-layer structure in which high-density layers and low-density layers are alternately laminated. The sound absorbing material is disclosed.
Note that Patent Document 1 discloses that the air permeability of the high-density layer is preferably 1 cc/cm ² ·sec or less for effective sound absorption performance in a low frequency region (500 Hz or less). In addition, in Examples 17 to 19, 22, 29, and 30 of Patent Document 1, a high density layer having a high airflow resistance per unit thickness and a low airflow resistance per unit thickness are provided as modes that satisfy this configuration. The low-density layers are laminated alternately, and the ventilation resistance per unit thickness of the high-density layers located on the surface of the sound absorbing material is better than the ventilation resistance per unit thickness of the high-density layers sandwiched between the low-density layers. Also disclosed is a sound absorbing material having a four-layer structure, which is small. The high-density layer in the example of Patent Document 1 is formed by heat-molding and compressing a nonwoven fabric manufactured by a melt-blowing method, and the low-density layer is formed by a nonwoven fabric manufactured by a melt-blowing method or a nonwoven fabric manufactured by a melt-spinning method.

JP-A-8-152890 (claims, 0014, examples, etc.)

However, the applicant of the present application refers to the above-described conventional technique (for example, the cited document 1) and regards the sound absorbing material having the four-layer structure as disclosed in Examples 17 to 19, 22, 29, and 30 described above. As a result of examination, there was a problem that the sound absorption performance was deteriorated in a high frequency band (for example, 4000 Hz or higher). Therefore, the sound absorbing material according to the related art is insufficient to achieve the purpose of improving quietness.

The present invention has been made under such circumstances, and an object of the present invention is to provide a sound absorbing material having more excellent sound absorbing performance.

The present invention is a sound absorbing material having a structure in which "first porous layer/second porous layer/third porous layer/fourth porous layer are laminated in this order, and the second porous layer Permeability resistance per unit thickness of the porous layer and the fourth porous layer is smaller than the ventilation resistance per unit thickness of the first porous layer, the unit thickness of the first porous layer Permeation resistance is smaller than the permeation resistance per unit thickness of the third porous layer, and the air permeability of the first porous layer and the third porous layer is 1 cm ³ /cm ² / sound absorbing material larger than s".

The inventors of the present invention are a sound absorbing material having a structure in which "first porous layer/second porous layer/third porous layer/fourth porous layer are laminated in this order, The ventilation resistance per unit thickness of the porous layer and the fourth porous layer is smaller than the ventilation resistance per unit thickness of the first porous layer, and the unit of the first porous layer is Air permeation resistance per thickness is smaller than air permeation resistance per unit thickness of the third porous layer.” In a sound absorbing material, the air permeability of the first porous layer and the third porous layer. It has been found that a sound absorbing material having excellent sound absorbing performance in a high frequency band (for example, 4000 Hz or higher) can be realized by having a configuration in which is greater than 1 cm ³ /cm ² /s.
Therefore, according to the present invention, it is possible to provide a sound absorbing material having more excellent sound absorbing performance.

4 is a graph summarizing the sound absorption coefficient exhibited by the sound absorbing materials prepared in Example 1 and Comparative Example 1. 5 is a graph summarizing the sound absorption coefficient exhibited by the sound absorbing materials prepared in Example 2 and Comparative Example 2. 7 is a graph summarizing the sound absorption coefficient exhibited by the sound absorbing materials prepared in Example 3 and Comparative Example 3. 5 is a graph summarizing the sound absorption coefficient exhibited by the sound absorbing materials prepared in Example 4 and Comparative Example 4. 6 is a graph summarizing the sound absorption coefficient exhibited by the sound absorbing materials prepared in Example 5 and Comparative Example 5. 7 is a graph summarizing the sound absorption coefficient exhibited by the sound absorbing materials prepared in Example 6 and Comparative Example 6. 7 is a graph summarizing the sound absorption coefficient exhibited by the sound absorbing materials prepared in Example 7 and Comparative Example 7. 9 is a graph summarizing the sound absorption coefficient exhibited by the sound absorbing materials prepared in Example 8 and Comparative Example 8. It is the graph which put together the sound absorption coefficient which the sound absorbing material prepared in Example 9-11 exhibited.

We have
Configuration 1: a structure in which a first porous layer/a second porous layer/a third porous layer/a fourth porous layer are laminated in this order, and a second porous layer and a fourth porous layer are provided. The ventilation resistance per unit thickness of the porous layer is smaller than the ventilation resistance per unit thickness of the first porous layer,
Configuration 2: The ventilation resistance per unit thickness of the first porous layer is smaller than the ventilation resistance per unit thickness of the third porous layer,
In the sound absorbing material having both configurations,
Configuration 3: the air permeability of the first porous layer and the third porous layer is greater than 1 cm ³ /cm ² /s,
It has been found that, by having such a configuration, the sound absorbing performance of the sound absorbing material in the high frequency band can be effectively improved, and the sound absorbing material having excellent sound absorbing performance can be provided.

The reason for this is not completely clear, but it is thought that the following effects are efficiently exhibited.
By satisfying the above configuration 1, when sound is repeatedly reflected between the first porous layer and the third porous layer in the sound absorbing material, the fourth porous layer side is in contact with the wall. In the provided sound absorbing material, when the sound is repeatedly reflected between the third porous layer and the wall, the sound is reflected on the constituent members such as the fibers forming the second porous layer and the fourth porous layer. The collision causes the sound energy to be converted into heat energy, whereby the sound is attenuated and absorbed.
Further, by satisfying the above configuration 2, the sound entering the sound absorbing material is less likely to pass through in the third porous layer as compared with the other porous layers, so that the sound is transmitted through the first porous layer. Between the second porous layer and the third porous layer, and between the third porous layer and the wall, and is easily reflected, and collides with the constituent members such as fibers forming the second porous layer and the fourth porous layer. By converting sound energy into heat energy, the sound is attenuated and the sound is absorbed.
And, by satisfying the above-mentioned configuration 3, the sound can easily pass through the first porous layer and the third porous layer, and the effects exhibited by the configurations 1 and 2 can be more efficiently exhibited. Conceivable.
It is considered that the structure of the present invention has the laminated structure of the high-density layer and the low-density layer, and therefore exerts the mass spring effect.

In the sound absorbing material of this configuration, when the air permeability of the first porous layer and the third porous layer is 1 cm ³ /cm ² /s or less, it is difficult for sound to enter the sound absorbing material and Since the sound absorbing performance may be deteriorated, it needs to be larger than 1 cm ³ /cm ² /s. If the air permeability of the first porous layer and the third porous layer is greater than 1 cm ³ /cm ² /s, it is adjusted appropriately so as to realize a sound absorbing material with excellent sound absorbing performance, as performance is effectively exhibited, the air ^{permeability,} 2cm 3 / ^cm 2 / s or more is more ^preferable, 4cm 3 / ^cm 2 / s or more further ^preferably, 7cm 3 / ^cm 2 / s or more preferable. On the other hand, the upper limit of the air permeability of the first porous layer and the third porous layer can be adjusted as appropriate, but if the air permeability of the first porous layer and the third porous layer is too large, the sound wave will be There is a possibility that the sound absorbing performance of the sound absorbing material may not be improved as intended due to the fact that the one porous layer and the third porous layer are made to be difficult to collide with the constituent member such as a fiber. The upper limit of the air permeability of the one porous layer and the third porous layer is preferably 1000 cm ³ /cm ² /s or less, more preferably 700 cm ³ /cm ² /s or less, and 500 cm ³ / More preferably, it is not more than cm ² /s.

The air permeability of the second porous layer and the fourth porous layer can be appropriately adjusted as long as this configuration is satisfied, but if the air permeability is too small, the sound hardly enters the sound absorbing material, and the sound absorbing performance of the sound absorbing material is reduced. On the other hand, if the air permeability is too large, the sound waves constitute the second porous layer and the fourth porous layer, for example, it is difficult to collide with the constituent members such as fibers. The sound absorbing performance of the sound absorbing material may not be improved as intended. The air permeability of the second porous layer and the fourth porous layer is larger than the air permeability of the first porous layer and the third porous layer so that the above-mentioned effects are effectively exhibited. It is preferably, specifically, 2.5 to 900 cm ³ /cm ² /s is preferable, 3.5 to 450 cm ³ /cm ² /s is more preferable, 60 to 200 cm ³ / More preferably, it is cm ² /s.

The air permeability in the present invention can be measured by using the air permeability measuring method described below.
(Method of measuring air permeability)
1. In accordance with JIS L1096:2010 "Fabricity test method for woven and knitted fabrics", "Fragrance" A method (Fragille type method), a Frazier type air permeability tester that can be used for measuring air permeability is prepared. In addition, in the Frazier-type air permeability tester, the size of the ventilation part is a circle having a diameter of 70 mm.
2. A measurement target (a breathable skin material or a breathable base material) is punched out, and a disc-shaped test piece having a diameter of 29 mm is collected.
3. A shape in which one end of a cylinder (outer diameter: 35 mm, inner diameter: 29 mm, height 20 mm) is connected and integrated in the center of a flat plate (length: 100 mm, width: 100 mm) having a circular opening with a diameter of 29 mm in the center. , Prepare the jig.
4. The test piece is housed inside the cylindrical part of the jig, and the O-ring (outer diameter: 29 mm, inner diameter: 25 mm) is arranged at the contact part between the cylindrical part and the test piece, so that the test can be performed with the cylindrical part when measuring the air permeability. Make sure there is no ventilation in the contact area of the strip.
5. The jig is installed on the ventilation part of the Frazier type air permeability tester such that the center of the ventilation part of the Frazier type air permeability tester and the center of the test piece stored in the jig overlap. At this time, ventilation should not be generated in the contact portion between the Frazier type air permeability tester and the jig.
6. The air permeability is measured under the condition that the differential pressure is 125 Pa. In addition, the ventilation part of the test piece at this time has a circular shape (inner peripheral shape of the O-ring) having a diameter of 25 mm.
7. The air permeability (unit: cm ³ /cm ² /s) of the measurement target is calculated by multiplying the measurement result by 7.84 and converting the result. In addition, 7.84 times is the value which divided the area of the ventilation part (diameter 70 mm) of the Frazier type air permeability tester by the area of the ventilation part (diameter 25 mm) of the test piece.

The thicker the thickness of the first porous layer and the third porous layer, the more likely it is to obtain a sound-absorbing material with excellent sound-absorbing performance, while if it is too thick, the sound-absorbing material will have poor handleability. Therefore, the thickness is preferably 0.01 to 1000 mm, more preferably 0.05 to 100 mm, still more preferably 0.1 to 10 mm. The "thickness" referred to here is the load on the measurement object when a load of 1.8 gf/cm ² is applied to the main surface from the main surface of the measurement object to the other main surface. Is the value measured by a high-precision digital length measuring machine in the direction of the action of. Further, in the present invention, the “main surface” is the widest surface of the measurement object.

Further, as for the basis weight of the first porous layer and the third porous layer, the heavier the weight, the more likely it is to be able to obtain a sound-absorbing material having excellent sound-absorbing performance. since there tends to be, it is preferably from 1 to 800 g / ^{m 2,} more preferably from 5~400g / ^{m 2,} and even more preferably 20~180g / ^{m 2.} In addition, the "area weight" in this invention means the mass per 1 m< ² > in the main surface of a measurement object.

As for the thickness of the second porous layer and the fourth porous layer, the thicker the thickness, the more likely it is to obtain a sound-absorbing material having excellent sound-absorbing performance. Therefore, the thickness is preferably 0.005 to 50 mm, more preferably 0.025 to 25 mm, and further preferably 0.1 to 10 mm.

Further, the areal weight of the second porous layer and the fourth porous layer, the heavier the heavier, the more likely it is to be able to obtain a sound-absorbing material with excellent sound-absorbing performance, while if it is too heavy, the handleability tends to deteriorate. since there is preferably from 20~3000g / ^{m 2,} more preferably from 40~1500g / ^{m 2,} and even more preferably 60~250g / ^{m 2.}

σ：単位厚さあたりの通気抵抗（単位：Ｎ・ｓ／ｍ^４）
ΔＰ：差圧（１２５Ｐａ）
Ｑ：通気度（単位：ｃｍ^３／ｃｍ^２／ｓ）
ｔ：厚さ（単位：ｍｍ） The "ventilation resistance per unit thickness" in the present invention is a value calculated by substituting the physical property values of each porous layer into the following formula.

σ: ventilation resistance per unit thickness (unit: N·s/m ⁴ )
ΔP: Differential pressure (125 Pa)
Q: Air permeability (unit: cm ³ /cm ² /s)
t: thickness (unit: mm)

Even if the sound absorbing material is one in which each porous layer is bonded and integrated by a binder or an adhesive component derived from an organic polymer, a sound absorbing material that can easily separate each porous layer or each porous layer is simply superposed. In the case of the sound absorbing material, the "permeation resistance per unit thickness" of each of the porous layers constituting the porous material obtained by separating from the sound absorbing material is subjected to the above-mentioned (method of measuring air permeability). It can be calculated from the value of the air permeability thus obtained and the value of the thickness measured by the above method.

On the other hand, the values of air permeability and thickness of each porous layer used for preparing the sound absorbing material are unknown, and each porous layer is caused by factors such as the presence of a binder or an adhesive component derived from an organic polymer and fiber bonding. In the sound-absorbing material that is difficult to obtain by separating the layers, the "ventilation resistance per unit thickness" of each porous layer that constitutes the sound-absorbing material is described below <Measurement of air permeability and thickness Method> From the air permeability value and thickness value obtained by
<Measurement method of air permeability and thickness>
1. Freeze the sound absorbing material with liquid nitrogen and cut the sound absorbing material in the direction perpendicular to the main surface.
2. The cross section of the sound absorbing material is analyzed (for example, visually, optical microscope, electron microscope, etc.) to confirm the presence or absence of the porous layer.
3. When the layers of the porous layer can be distinguished, the porous layer is cut from the sound absorbing material and a test piece is collected. When two adjacent porous layers are adhered by the adhesive component that adheres each porous layer, the boundary between the region having the adhesive component and the region not having the adhesive component is the layer between the adjacent porous layers. And collect the test piece. Among the adjacent porous layers, which of the porous layers should contain the region having the adhesive component is determined by the following method to obtain the ventilation resistance per unit thickness of the two porous layers, and The porous layer having a high ventilation resistance per unit thickness is made to include a region having an adhesive component.
First, the two porous layers are separated by removing the region having the bonded portion from the two adjacent porous layers bonded by the adhesive component. Next, the air permeability is subjected to the above-mentioned (measuring method of air permeability) to measure the thicknesses of the two separated porous layers by the above-mentioned method, and the air-flow resistance per unit thickness is obtained.
4. The thickness of the porous layer is measured by measuring the thickness of the test piece to be measured by the method described above. Then, the test piece is subjected to the above-mentioned (method of measuring air permeability) to measure air permeability.
In addition, when the sound absorbing material is made of cloth and the cross section of the sound absorbing material is analyzed to confirm the presence or absence of the porous layer, when the interlayer between the adjacent porous layers is unclear, the following method is used. Judge the layers.
(1) A fiber that analyzes one main surface of the sound absorbing material, identifies the largest number of fibers (A) present on the one main surface, and occupies the number of fibers present on the one main surface The percentage of the number of (A) is calculated.
(2) Take a cross-sectional photograph of the sound absorbing material.
(3) Innumerable parallel lines which are substantially parallel to the main surface of the sound absorbing material are drawn on the photograph of the cross section of the sound absorbing material, and the ratio of the fiber A to the number of fibers having an intersection with the parallel line is calculated in (1). Among the lines having 50% or more of the percentage of the number of the fibers A, the line showing the smallest value is defined as the layer of the porous layer.
(4) From the one main surface to the layer of the porous layer is regarded as the first porous layer, the first porous layer is cut out from the sound absorbing material, and a test piece is collected.
(5) The above 4. The thickness and air permeability of the test piece (porous layer) are measured in the same manner as in.
In addition, when the layers of the adjacent porous layers are unclear even after the second layer,
<1> The main surface on the side where the first porous layer of the sound absorbing material is cut off is analyzed, and the largest number of fibers in the number of fibers (A) subtracted from the number of fibers present on the main surface is analyzed. Determine the percentage of high fiber (B).
<2> In the same manner as in the above (2) to (3), a line which is 50% of the percentage of the number of the fibers (B) obtained in <1> is defined as the interlayer of the porous layer.
<3> In the same manner as in the above (4) to (5), the area to be regarded as the second porous layer is determined, and the thickness and air permeability of each of the collected test pieces (porous layer) are determined. taking measurement.
<4> From the other main surface of the sound absorbing material, find the layers between the porous layers in the same manner, sample each porous layer that constitutes the sound absorbing material, and measure each thickness and each air permeability. To do.

First porous layer, second porous layer, third porous layer, fourth porous layer (hereinafter, the porous layer may be collectively referred to as "each porous layer" There is no particular limitation as to the type of a), but for example, a non-woven fabric, a woven fabric (for example, a mesh), a knitted fabric, a breathable perforated film or a foam sheet may be used. It can be a contained structure. In particular, it has excellent workability and followability when used as a sound-absorbing material, and since it is easy to exert the effect of preventing the deterioration of sound-absorbing performance due to the occurrence of unintentional deformation during processing or installation, each porous The layer is preferably a cloth, and it is more preferable that each porous layer is a non-woven fabric because the above-mentioned effects are more easily exhibited.

Each porous layer is, for example, a polyolefin resin (for example, polyethylene, polypropylene, polymethylpentene, a polyolefin resin having a structure in which a part of hydrocarbon is replaced with a cyano group or a halogen such as fluorine or chlorine), a styrene resin. , Polyvinyl alcohol resins, polyether resins (for example, polyether ether ketone, polyacetal, modified polyphenylene ether, aromatic polyether ketone, etc.), polyester resins (for example, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, Polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, wholly aromatic polyester resin, etc., polyimide resin, polyamideimide resin, polyamide resin (for example, aromatic polyamide resin, aromatic polyetheramide resin, nylon resin) Etc.), a resin having a nitrile group (for example, polyacrylonitrile, etc.), a urethane resin, an epoxy resin, a polysulfone resin (for example, polysulfone, polyether sulfone, etc.), a fluorine resin (for example, polytetrafluoroethylene, polyfluorine). Vinylidene chloride), cellulosic resin, polybenzimidazole resin, acrylic resin (for example, polyacrylonitrile resin copolymerized with acrylic acid ester or methacrylic acid ester, modacrylic resin copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride) A known organic polymer such as a resin) may be used.

Incidentally, these organic polymers may be composed of either a linear polymer or a branched polymer, the organic polymer may be a block copolymer or a random copolymer, and the three-dimensional structure or crystal of the organic polymer. The presence or absence of sex is not particularly limited. Further, it may be a mixture of multi-component organic polymers and is not particularly limited.

When a sound absorbing material having excellent flame retardancy is required, such as when the sound absorbing material is used for electric appliances such as automobiles and office automation equipment, each porous layer contains a flame retardant organic polymer. It is preferable to go out. Examples of such flame-retardant organic polymers include modacrylic resins, vinylidene resins, polyvinyl chloride resins, polyvinylidene fluoride resins, novoloid resins, polyclar resins, polyester resins obtained by copolymerizing phosphorus compounds, and halogen-containing monomers. Examples thereof include acrylic resins, aramid resins, and resins in which a halogen-based, phosphorus-based, or metal compound-based flame retardant is kneaded.

Further, in order to improve the sound absorbing performance of the sound absorbing material, each porous layer is provided with, for example, silica particles or hollow particles, an adhesive component that adheres the constituent members of each porous layer, and the like. The ventilation resistance per unit thickness may be adjusted. In particular, by providing each porous layer with thermally expandable hollow particles and an adhesive component, the ventilation resistance per unit thickness can be adjusted. The term "hollow particles" as used herein refers to particles having a gas inside.

When each porous layer is a cloth, the constituent fibers include, for example, melt spinning method, dry spinning method, wet spinning method, direct spinning method (melt blow method, spun bond method, electrostatic spinning method, etc.), and composite fiber. It can be obtained by a known method such as a method of extracting fibers having a small fiber diameter by removing more than one kind of resin component or a method of beating the fibers to obtain divided fibers.

The fibers constituting the cloth may be composed of one type of organic polymer or may be composed of a plurality of types of organic polymers. Fibers composed of a plurality of types of organic polymers can be in the form of generally called conjugate fibers, for example, core-sheath type, sea-island type, side-by-side type, orange type, bimetal type and the like. In particular, it is preferable that the latent crimped fiber, which is a side-by-side type composite fiber, is included because a porous layer having high ventilation resistance per unit thickness can be provided.
The fabric may include adhesive fibers as constituent fibers. By including the adhesive fiber, the compression hardness of the fabric can be adjusted to effectively improve the sound absorbing performance of the sound absorbing material, and also, the separation of the fiber from the fabric is suppressed, and the sound absorbing due to the unintentional deformation occurs. It is preferable because it is possible to prevent deterioration of performance. The type of the adhesive fiber is appropriately selected, but, for example, core-sheath type adhesive fiber, side-by-side type adhesive fiber, or all-melt type adhesive fiber can be adopted.

Further, the fabric may include fibers having an irregular cross-section as the constituent fibers in addition to the fibers having a substantially circular cross section and the elliptical shape. As the modified cross-section fiber, a polygonal shape such as a triangular shape, an alphabetic character shape such as a Y shape, an irregular shape, a multileaf shape, a symbolic shape such as an asterisk shape, or a shape formed by combining a plurality of these shapes A fiber having a fiber cross section such as

When the cloth is woven or knitted, it can be prepared by weaving or knitting the fibers prepared as described above.

When the cloth is a non-woven fabric, as the non-woven fabric, for example, a dry non-woven fabric in which fibers are entangled to form a non-woven fabric by being subjected to a card device, an air-laying device, etc. Wet non-woven fabric, direct spinning method (melt blow method, spun bond method, electrostatic spinning method, spinning method by discharging a spinning stock solution and a gas stream in parallel (for example, the method disclosed in JP-A-2009-287138)) ) Is used to spun the fiber and the non-woven fabric is obtained by collecting the spun fiber. Further, since the degree of entanglement of fibers in the non-woven fabric is adjusted, the non-woven fabric can be supplied to a needle punch device or a hydroentangling device.

Among the respective porous layers of the present invention, when the first porous layer and the third porous layer are cloth, the average fiber of the constituent fibers of the first porous layer and the third porous layer The smaller the diameter, the more likely it is that a sound absorbing material with excellent sound absorbing performance can be obtained. Therefore, the average fiber diameter of the fibers forming the first porous layer and the third porous layer is, for example, preferably 100 μm or less, more preferably 40 μm or less, and 4 μm or less. More preferable. The lower limit value is appropriately adjusted, but it is realistic that the lower limit value is 0.1 μm or more. From the viewpoint that it is easy to obtain a thin average fiber diameter, it is preferable that the first porous layer and the third porous layer are non-woven fabrics prepared by the direct spinning method, and the thin average fiber diameter is, and It is a melt blown non-woven fabric prepared by the melt blow method because it is easy to obtain the first porous layer and the third porous layer having high ventilation resistance per unit thickness, and a sound absorbing material having excellent sound absorbing performance can be realized. Is more preferable. Further, since the ventilation resistance per unit thickness of the first porous layer is easily smaller than the ventilation resistance per unit thickness of the third porous layer, the first porous layer The average fiber diameter of the fibers forming the third porous layer is preferably smaller than the average fiber diameter of the fibers forming the third porous layer.
In the present invention, the “average fiber diameter” means 100 fibers randomly selected by analyzing an electron micrograph of a cross section of a structure containing fibers (such as a porous layer containing fibers). It is the arithmetic mean value of the diameter, and the fiber diameter means the diameter of a circle having the same area as the cross-sectional area of the fiber.

The fiber length of the fibers forming the first porous layer and the third porous layer is not particularly limited, but can be 0.1 to 150 mm, and depending on the method for producing the fibers, continuous fibers can be used. Can also be It should be noted that two or more kinds of fibers different in the average fiber diameter and/or the fiber length may be included. In the present invention, the “fiber length” means the length measured by the method defined in JIS L 1015 (Chemical fiber staple test method): 2010, method B (corrected staple diagram method) in Section 8.4. To do. Further, a fiber having a fiber length of more than 150 mm is regarded as a continuous fiber.

Among the porous layers of the present invention, when the second porous layer and the fourth porous layer are cloth, the average fiber diameter of the constituent fibers of the second porous layer and the fourth porous layer The fineness is not particularly limited as long as the structure of the present invention is satisfied, but when the second porous layer and the fourth porous layer are dry nonwoven fabrics, a sound absorbing material having excellent sound absorbing performance is provided. As it can be obtained, it is preferably 0.05 to 100 dtex, more preferably 0.5 to 50 dtex, and further preferably 0.7 to 15 dtex. The fiber length is also not particularly limited, but may be 0.1 to 150 mm, and may be continuous fiber depending on the fiber manufacturing method. It should be noted that two or more kinds of fibers which differ in fineness and/or fiber length may be included.

The lamination mode of the respective porous layers is appropriately adjusted, and it may be a sound absorbing material in which the respective porous layers are simply superposed or a sound absorbing material in which the respective porous layers are bonded and integrated with a binder interposed therebetween. When each porous layer is a cloth, it may be a sound absorbing material in which an organic polymer that constitutes fibers such as adhesive fibers contained in the cloth is melted and laminated and integrated.

The type of binder is appropriately adjusted, and the above-mentioned organic polymer can be used as the binder. Further, the mode of the binder that adheres each porous layer can be appropriately adjusted. Even if each porous layer is adhered by a dot-shaped binder, a spider web-shaped (web-shaped) binder can be used. Alternatively, the laminated porous layers may be impregnated with a binder solution and dried to be bonded with the binder.

In particular, when each porous layer is bonded with a spider web-shaped (web-shaped) binder, the binder existing between the porous layers is unlikely to affect the air permeability of each porous layer. Since the air permeability between the layers tends not to be lowered, it is a sound absorbing material that exhibits excellent sound absorbing performance in a wide frequency band such as a high frequency band of 4000 Hz or higher, which is preferable.

The mass of the binder adhering each porous layer is appropriately adjusted, but it is preferably 0.5 to 30 g/m ² , and especially the mass of the adhesive component adhering each porous layer is When it is in the range of 1.0 to 10 g/m ² , the adhesive component present in each porous layer is unlikely to affect the air permeability of each porous layer, and the air permeability between each porous layer tends not to be lowered. Therefore, for example, it is a sound absorbing material that exhibits excellent sound absorbing performance in a wide frequency band such as a high frequency band of 4000 Hz or more, which is more preferable.

Various configurations of the sound absorbing material, such as thickness, basis weight, and air permeability, are not particularly limited, and are appropriately adjusted so as to have excellent sound absorbing performance.

The thickness of the sound absorbing material is preferably 4 to 300 mm, more preferably 8 to 150 mm, and further preferably 10 to 50 mm.

Also, the basis weight of the sound absorbing material, for example, is preferably from 40~7600g / ^{m 2,} more preferably from 90~3800g / ^{m 2,} and even more preferably 160~450g / ^{m 2.}

The air permeability of the sound absorbing material is preferably from 0.5~400cm ³ / ^cm 2 / s, more preferably from ^{0.9~160cm 3 / cm 2 / s,} 3~60cm 3 / cm More preferably, it is ² /s.

The sound absorbing material of the present invention is a laminate of at least a first porous layer, a second porous layer, a third porous layer, and a fourth porous layer, for improving sound absorbing performance. Another porous layer may be laminated.

The laminate obtained by laminating the porous layers as described above can be used as it is as a sound absorbing material, but for the purpose of imparting durability, rigidity or flame retardancy, for example, non-woven fabric, woven fabric (for example, mesh, etc.), knitted fabric, etc. A separately prepared member such as the cloth, a breathable film or a foam sheet may be laminated. For the purpose of imparting flame retardancy, it is preferable to employ, as a separately prepared member, for example, a fabric containing flame retardant fibers or a flame retardant.

The separately prepared member can be laminated on the exposed main surface of the first porous layer and/or the fourth porous layer in the laminate, but the sound absorbing effect of the sound absorbing material is effectively exhibited. Thus, since it is preferable to provide a sound absorbing material so that the first porous layer side faces the side where the sound wave to be sound-absorbed is present, the exposed main surface of the first porous layer in the laminate. It is preferable to stack a separately prepared member on top.

In addition, since the sound absorbing material thus prepared is used by being attached to a wall surface or the inside of a device, an adhesive or a double-sided adhesive tape is provided on the main surface of the sound absorbing material opposite to the side where the sound wave to be absorbed exists. Or a surface fastener may be provided.

The shape of the sound absorbing material can be appropriately adjusted and is not limited, and may be, for example, a round shape, an oval shape, a square shape, a rectangular shape, or the like. Further, for example, it may have a desired shape such as corrugated, pleated, wound, cut out, punched, punched, or partially cut.

The manufacturing method of the sound absorbing material can be appropriately selected, but as an example of the manufacturing method, a plurality of card machines are prepared in advance. For example, latent crimped fibers are provided in the first and third layers, and first and third layers in the fourth and fourth layers. A fibrous web is prepared by laminating a fibrous structure using fibers having a crimping degree lower than that of the fibers contained in the eyes (for example, a cross wrapper can be used), and by heat treatment, the first porous You may manufacture the sound absorbing material of this invention which has layer / 2nd porous layer / 3rd porous layer / 4th porous layer. With this manufacturing method, a sound absorbing material containing no adhesive component can be easily prepared.

Hereinafter, the present invention will be described in detail with reference to Examples, but these do not limit the scope of the present invention.

(Examples 1-3, Comparative Example 1)
(Preparation of Nonwoven Fabric Constituting First Porous Layer and Third Porous Layer)
Melt blown non-woven fabric A-H (hereinafter, the melt blown non-woven fabric may be referred to as MB non-woven fabric) was prepared by using a melted polypropylene resin as a spinning solution and spinning and collecting the melted polypropylene resin by a melt blow method.
MB non-woven fabric A (average fiber diameter: 4.9 μm, air permeability: 120 cm ³ /cm ² /s, thickness: 1.4 mm, air resistance per unit thickness: 7.4×10 ⁴ N·s/m ⁴ , unit weight: 78 g/m ² )
MB non-woven fabric B (average fiber diameter: 2.3 μm, air permeability: 20 cm ³ /cm ² /s, thickness: 1.3 mm, ventilation resistance per unit thickness: 4.8×10 ⁵ N·s/m ⁴ , unit weight: 78 g/m ² )
MB non-woven fabric C (average fiber diameter: 30.1 μm, air permeability: 410 cm ³ /cm ² /s, thickness: 1.3 mm, ventilation resistance per unit thickness: 2.3×10 ⁴ N·s/m ⁴ , unit weight: 78 g/m ² )
MB non-woven fabric D (average fiber diameter: 3.9 μm, air permeability: 80 cm ³ /cm ² /s, thickness: 1.2 mm, ventilation resistance per unit thickness: 1.3×10 ⁵ N·s/m ⁴ , unit weight: 78 g/m ² )
MB non-woven fabric E (average fiber diameter: 1.9 μm, air permeability: 30 cm ³ /cm ² /s, thickness: 0.5 mm, ventilation resistance per unit thickness: 8.3×10 ⁵ N·s/m ⁴ , unit weight: 20 g/m ² )
MB non-woven fabric F (average fiber diameter: 1.9 μm, air permeability: 7 cm ³ /cm ² /s, thickness: 0.1 mm, airflow resistance per unit thickness: 1.8×10 ⁷ N·s/m ⁴ , unit weight: 20 g/m ² )
MB non-woven fabric G (average fiber diameter: 2.3 μm, air permeability: 18 cm ³ /cm ² /s, thickness: 10 mm, ventilation resistance per unit thickness: 6.9×10 ⁴ N·s/m ⁴ , Unit weight: 160g/m ² )
MB non-woven fabric H (average fiber diameter: 1.9 μm, air permeability: 10 cm ³ /cm ² /s, thickness: 10 mm, ventilation resistance per unit thickness: 1.3×10 ⁵ N·s/m ⁴ , Unit weight: 160g/m ² )

(Preparation of Nonwoven Fabric Forming Second Porous Layer and Fourth Porous Layer)
(Preparation of dry non-woven fabric a)
A fiber group in which 75% by mass of polyethylene terephthalate fiber A (fineness: 2.2 dtex, fiber length: 56 mm) and 25% by mass of low melting point polyethylene terephthalate fiber (fineness: 4.4 dtex, fiber length: 51 mm) are mixed into a card machine. Then, a dry web was prepared by stacking with a cross wrapper.
Then, the dry web is heat-treated at 170° C. to melt the low melting point polyethylene terephthalate fiber, and the dry non-woven fabric a (air permeability: 177 cm ³ /cm ² /s, thickness: 12 mm, ventilation resistance per unit thickness: 5). 1.9×10 ³ N·s/m ⁴ and basis weight: 100 g/m ² ) were prepared.
(Preparation of MB non-woven fabric I)
MB non-woven fabric I (average fiber diameter: 1.9 μm, air permeability: 12 cm ³ /cm ² /s, thickness, obtained by using a melted polypropylene resin as a spinning solution and spinning and collecting using a melt blow method : 12 mm, ventilation resistance per unit thickness: 8.7×10 ⁴ N·s/m ⁴ , and basis weight: 160 g/m ² ) were prepared.
(Preparation of dry non-woven fabric b)
The dry non-woven fabric b (air permeability: the same as the dry non-woven fabric a) except that the polyethylene terephthalate fiber B (fineness: 14.4 dtex, fiber length: 64 mm) was used instead of the polyethylene terephthalate fiber A, and the basis weight was different. 263 cm ³ /cm ² /s, thickness: 12 mm, ventilation resistance per unit thickness: 4.0×10 ³ N·s/m ⁴ , and basis weight: 70 g/m ² ) were prepared.
(Preparation of dry non-woven fabric c)
Dry non-woven fabric c (air permeability: 524 cm ³ /cm ² /s, thickness: 6 mm, ventilation resistance per unit thickness: 4.0×10 ³ N, similar to dry non-woven fabric b) except that the basis weight is different. · s / ^{m 4,} basis weight: 40g / ^{m 2)} was prepared.
(Preparation of dry nonwoven fabric d)
Similar to the dry non-woven fabric b, the dry non-woven fabric d (air permeability: 154 cm ³ /cm ² /s, thickness: 20 mm, ventilation resistance per unit thickness: 4.0×10 ³ N) except that the basis weight is different. · s / ^{m 4,} basis weight: 110g / ^{m 2)} was prepared.
(Preparation of dry nonwoven fabric e)
The dry non-woven fabric e (air permeability: 210 cm ³ /cm ² /s, thickness: 12 mm, air permeation resistance per unit thickness: 5.0×10 ³ N) except that the basis weight is different. · s / ^{m 4,} basis weight: 70g / ^{m 2)} was prepared.
(Preparation of dry nonwoven fabric f)
The dry non-woven fabric f (air permeability: 170 cm ³ /cm ² ) is the same as the dry non-woven fabric e except that the polyethylene terephthalate fiber C (fineness: 0.8 dtex, fiber length: 38 mm) is used instead of the polyethylene terephthalate fiber A. /S, thickness: 12 mm, ventilation resistance per unit thickness: 6.1×10 ³ N·s/m ⁴ , and basis weight: 70 g/m ² ) were prepared.
(Preparation of dry non-woven fabric g)
The dry nonwoven fabric g (air permeability: 64 cm ³ /cm ² /s, thickness: 12 mm, ventilation resistance per unit thickness: 1.6×10 ⁴ N, similar to the dry nonwoven fabric f, except that the basis weight is different. .S/m ⁴ , basis weight: 200 g/m ² ) was prepared.

(Preparation of sound absorbing material)
The non-woven fabrics were laminated in the combinations shown in Table 1 without adhering to each other to prepare a sound absorbing material having a four-layer structure.

Table 1 shows the types of porous layers (nonwoven fabrics) constituting the sound absorbing materials of Examples and Comparative Examples, and the basis weight and thickness of the sound absorbing material.

(Measurement of sound absorption performance)
A circular test piece having a diameter of 29 mm was sampled from each of the sound absorbing materials prepared as described above.
Then, each test piece is subjected to a measurement method in accordance with JIS A1405-1:2007, and the normal incidence sound absorption coefficient (%) of each test piece is measured to obtain the sound absorption coefficient of each sound absorbing material in the frequency band of 500 to 6300 Hz. The behavior was measured. During the measurement of the test piece, a sound absorbing material was placed on the sound source side so that the first porous layer faced.

In the frequency band of 500 to 6300 Hz, the sound absorption coefficient exhibited by each of the prepared sound absorbing materials was summarized, and the data thus summarized was graphed and shown in FIGS.

From the results of FIGS. 1 and 2, in the sound absorbing materials of Examples 1 and 2 having the configuration of the present invention, the ventilation resistance per unit thickness of the second porous layer and the fourth porous layer was It was found that the sound absorbing performance in the high frequency band is excellent as compared with the sound absorbing materials of Comparative Examples 1 and 2 which have a larger air flow resistance per unit thickness of the porous layer.

Further, from the results of FIG. 3, in the sound absorbing material of Example 3 having the configuration of the present invention, Comparative Example 3 in which the first porous layer and the third porous layer have the same ventilation resistance per unit thickness It was found that the sound absorbing performance in the high frequency band is superior to that of the sound absorbing material of No.

Further, from the results of FIGS. 4 to 8, the sound absorbing materials of Examples 4 to 8 having the configuration of the present invention have a unit of the third porous layer rather than a ventilation resistance per unit thickness of the first porous layer. It was found that the sound absorbing performance in the high frequency band was superior to the sound absorbing materials of Comparative Examples 4 to 8 in which the ventilation resistance per thickness was smaller.

Furthermore, from the results of the sound absorbing materials of Examples 9 to 11 in FIG. 9, even if the compositions (area weight, thickness, air permeability, etc.) of the second porous layer and the fourth porous layer are different, the same results are obtained. Since the sound absorbing performance is exhibited, it was found that excellent sound absorbing performance in the high frequency band is exhibited by satisfying the configuration according to the present invention.

Then, all of the above-described examples satisfy the configurations 1 and 2, and the air permeability of the first porous layer and the third porous layer is larger than 1 cm ³ /cm ² /s. By satisfying (Structure 3), the sound absorbing material has excellent sound absorbing performance in the high frequency band.

The sound absorbing material of the present invention can be used as an industrial material required to have sound absorbing performance.
Therefore, for example, applications for reducing the sound generated inside and outside buildings such as general houses, factories, offices or hospitals, applications for reducing the sound generated inside and outside vehicles such as aircraft, ships, railway vehicles and automobiles, or for industrial use. It can be preferably used for the purpose of reducing the operation sound generated inside equipment such as robots, processing machines, medical equipment or information equipment equipment (for example, televisions, personal computers, printers or scanners).

Claims (1)

A sound-absorbing material having a structure in which a first porous layer/a second porous layer/a third porous layer/a fourth porous layer are laminated in this order, and the second porous layer and the second porous layer Air permeation resistance per unit thickness of the four porous layers is smaller than air permeation resistance per unit thickness of the first porous layer, the air permeation resistance per unit thickness of the first porous layer is , Smaller than the ventilation resistance per unit thickness of the third porous layer, and the air permeability of the first porous layer and the third porous layer is larger than 1 cm ³ /cm ² /s, Sound absorbing material.

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