WO2018154864A1 - 吸音材 - Google Patents

吸音材 Download PDF

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Publication number
WO2018154864A1
WO2018154864A1 PCT/JP2017/040232 JP2017040232W WO2018154864A1 WO 2018154864 A1 WO2018154864 A1 WO 2018154864A1 JP 2017040232 W JP2017040232 W JP 2017040232W WO 2018154864 A1 WO2018154864 A1 WO 2018154864A1
Authority
WO
WIPO (PCT)
Prior art keywords
layer
absorbing material
porous layer
sound
porous
Prior art date
Application number
PCT/JP2017/040232
Other languages
English (en)
French (fr)
Inventor
康介 細田
快 岡原
Original Assignee
日東電工株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日東電工株式会社 filed Critical 日東電工株式会社
Priority to US16/486,325 priority Critical patent/US20200234686A1/en
Priority to CN201780087477.XA priority patent/CN110337689A/zh
Priority to KR1020197024620A priority patent/KR20190125976A/ko
Priority to EP17897408.5A priority patent/EP3588487A4/en
Publication of WO2018154864A1 publication Critical patent/WO2018154864A1/ja

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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
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    • G—PHYSICS
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    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/321—Physical
    • G10K2210/3224—Passive absorbers

Definitions

  • the present invention relates to a sound absorbing material.
  • fiber materials such as glass wool and foam materials such as urethane foam have been widely used as sound absorbing materials.
  • these materials have poor low-frequency sound absorption, and it is necessary to use a thick material in order to obtain sufficient sound absorption at low frequencies.
  • a method using a plate and a film and a method of configuring a Helmholtz resonator using a slit and a perforated plate.
  • a method for constructing a Helmholtz resonator is often employed.
  • the perforated plate has a problem that the weight is large and a degree of freedom in shape is limited.
  • Patent Document 1 A sound-absorbing material in which a porous sheet such as foamed plastic and a dense sheet having through holes are alternately laminated has been reported (Patent Document 1). However, since this sound absorbing material requires a relatively thick dense sheet, it is difficult to achieve both low-frequency sound absorption and light weight.
  • An object of the present invention is to provide a sound-absorbing material that is thin and lightweight and excellent in low-frequency sound absorption.
  • the sound absorbing material of the present invention is A sound absorbing material having a laminated structure including a first perforated layer, a first porous layer, a second perforated layer, and a second porous layer in this order,
  • the first perforated layer has a plurality of through holes in the thickness direction;
  • the second perforated layer has a plurality of through holes in the thickness direction;
  • the thickness of the first perforated layer is less than 1 mm.
  • the maximum hole diameter of the plurality of surface openings of the first perforated layer formed by the plurality of through holes of the first perforated layer is 1 mm or more.
  • the surface opening ratio which is the ratio of the plurality of surface opening portions to the entire surface of the first perforated layer, is 20% or less.
  • the maximum hole diameter of the plurality of surface openings of the second perforated layer formed by the plurality of through holes of the second perforated layer is 1 mm or more.
  • the surface opening ratio which is the ratio of the plurality of surface opening portions to the entire surface of the second perforated layer, is 20% or less.
  • the thickness of the second perforated layer is less than 1 mm.
  • the thickness of the first porous layer is 1 mm or more.
  • the thickness of the second porous layer is 1 mm or more.
  • the overall thickness is less than 300 mm.
  • the first porous layer when the thickness of the first porous layer is D1, the first porous layer has a length of at least D1 in the thickness direction from at least one surface of the first porous layer.
  • the maximum pore diameter of the plurality of surface openings of the first porous layer that has a plurality of holes and is formed by the plurality of holes is 1 mm or more.
  • the plurality of surface openings of the first porous layer and the plurality of surface openings of the first perforated layer are arranged at a position where they overlap in a plan view.
  • the second porous layer when the thickness of the second porous layer is D2, the second porous layer is formed with a length of D2 or less in the thickness direction from at least one surface of the second porous layer.
  • the maximum pore diameter of the plurality of surface openings of the second porous layer that has a plurality of holes and is formed by the plurality of holes is 1 mm or more.
  • the plurality of surface openings of the second porous layer and the plurality of surface openings of the second perforated layer are disposed at a position where they overlap in a plan view.
  • the material constituting the first perforated layer is at least one selected from resin, metal, rubber, inorganic material, woven fabric, and non-woven fabric.
  • the material constituting the second perforated layer is at least one selected from resin, metal, rubber, inorganic material, woven fabric, and non-woven fabric.
  • the material constituting the first porous layer is a polymer porous body, a metal porous body, an inorganic porous body, a woven cloth porous body, a nonwoven fabric porous body, a fibrous material, a high It is at least one selected from molecular monoliths.
  • the material constituting the second porous layer is a polymer porous body, a metal porous body, an inorganic porous body, a woven cloth porous body, a nonwoven fabric porous body, a fibrous material, a high It is at least one selected from molecular monoliths.
  • FIG. 5 is a graph showing the sound absorption rate of sound absorbing materials (1) to (4).
  • FIG. 6 is a graph showing the sound absorption rate of sound absorbing materials (5) to (8). It is a graph which shows the sound absorption rate of a sound-absorbing material (C1).
  • FIG. 4 is a graph showing the sound absorption rate of sound absorbing materials (C2) to (C5).
  • the “perforated layer” means a layer having holes (through holes) penetrating in the thickness direction of the layer.
  • the “porous layer” means a layer having a plurality of voids (porous).
  • the sound absorbing material of the present invention has a laminated structure including a first perforated layer, a first porous layer, a second perforated layer, and a second porous layer in this order.
  • the sound-absorbing material of the present invention includes any appropriate other layer as long as it has a laminated structure including the first perforated layer, the first porous layer, the second perforated layer, and the second porous layer in this order. Also good.
  • Such other layers may have, for example, one or more through holes.
  • Each of the first perforated layer, the first porous layer, the second perforated layer, and the second porous layer may be a single layer or a laminate of two or more layers.
  • the sound absorbing material of the present invention preferably has a laminated structure including the first perforated layer, the first porous layer, the second perforated layer, and the second porous layer in this order, and the first perforated layer is the outermost layer. .
  • FIG. 1 is a schematic sectional view showing one embodiment of the sound absorbing material of the present invention.
  • a sound absorbing material 100 of the present invention has a first perforated layer 10A, a first porous layer 10B, a second perforated layer 20A, and a second porous layer 20B.
  • the first perforated layer 10A and the second porous layer 20B are the outermost layers.
  • the through holes of the first perforated layer 10A and the second perforated layer 20A and the pores of the first porous layer 10B and the second porous layer 20B are omitted without being shown.
  • FIG. 2 is a schematic sectional view showing one more specific embodiment of the sound absorbing material of the present invention.
  • the sound absorbing material 100 of the present invention has a first perforated layer 10A, a first porous layer 10B, a second perforated layer 20A, and a second porous layer 20B.
  • the first perforated layer 10A and the second porous layer 20B are the outermost layers.
  • the first perforated layer 10A has a plurality of through holes 1a in the thickness direction.
  • the second perforated layer 20 ⁇ / b> A has a plurality of through holes 2 a in the thickness direction.
  • the porosity of the first porous layer 10B and the second porous layer 20B is not shown and is omitted.
  • the through hole 1 a and the through hole 2 a are all disposed at positions where they overlap each other in plan view, but may be disposed at positions where some do not overlap, or at positions where all do not overlap. It may be arranged.
  • FIG. 3 is a schematic sectional view showing one more specific embodiment of the sound absorbing material of the present invention.
  • the sound absorbing material 100 of the present invention has a first perforated layer 10A, a first porous layer 10B, a second perforated layer 20A, and a second porous layer 20B.
  • the first perforated layer 10A and the second porous layer 20B are the outermost layers.
  • the sound-absorbing material 100 of the present invention has through holes 3 extending from the surface of the first porous layer 10A opposite to the first porous layer 10B to the surface of the second porous layer 20B opposite to the second porous layer 20A.
  • a plurality The porosity of the first porous layer 10B and the second porous layer 20B is not shown and is omitted.
  • the total thickness of the sound absorbing material of the present invention is preferably less than 300 mm, more preferably 1 mm to 200 mm, still more preferably 3 mm to 100 mm, and particularly preferably 5 mm to 50 mm. If the total thickness of the sound absorbing material of the present invention is within the above range, the sound absorbing material becomes a thin sound absorbing material and can be used for various purposes for which a thin sound absorbing material is required.
  • the average density of the sound absorbing material of the present invention is preferably 300 kg / m 3 or less, more preferably 1 kg / m 3 to 200 kg / m 3 , and still more preferably 5 kg / m 3 to 150 kg / m 3 , Particularly preferred is 10 kg / m 3 to 100 kg / m 3 , and most preferred is 20 kg / m 3 to 50 kg / m 3 . If the density of the sound-absorbing material of the present invention is within the above range, a light-absorbing material that is lighter and has excellent sound-absorbing properties at low frequencies can be provided.
  • the sound absorbing material of the present invention may be an embodiment in which the first perforated layer 10A does not cover up to the side surface, or in the perspective view of FIG. 4 (b).
  • the first perforated layer 10A may cover the middle of the side surface, and as shown in the perspective view of FIG. 4C, the first perforated layer 10A covers the entire side surface.
  • the first perforated layer 10A may be an embodiment in which the entire side surface and a part of the back surface are covered, or the perspective view of FIG.
  • the first perforated layer 10A may cover the entire side surface and the entire back surface. Further, in the embodiment shown in FIGS.
  • the embodiment may be a layer different from the one perforated layer 10A.
  • At least a part of the end surface in the length direction of the sound-absorbing material of the present invention may be blocked by any appropriate layer as long as the effect of the present invention is not impaired. Further, the end surface in the length direction of the sound absorbing material of the present invention may be blocked by a cross-sectional shape being deformed by a press or the like.
  • the sound-absorbing material of the present invention is thin and light and has excellent low-frequency sound absorption, and can be used in various applications.
  • the sound-absorbing material of the present invention can exhibit a very excellent sound-absorbing property in a low-frequency region, and can be employed, for example, as a tire sound-absorbing material, particularly as a countermeasure for cavity resonance noise.
  • the sound-absorbing material of the present invention is employed as a tire sound-absorbing material, it is preferable to exhibit excellent sound-absorbing properties in the region of 200 Hz to 300 Hz.
  • the sound-absorbing property in the tire can be expressed, preferably, FIG. 4 (b), FIG. 4 (c), FIG. 4 (e), more preferably the embodiment shown in FIG. 4 (c), FIG. 4 (d), and FIG. 4 (e).
  • the sound absorbing material of the present invention When the sound absorbing material of the present invention is used as a sound absorbing material for tires, either the first perforated layer side or the second porous layer side may be installed on the tire side, and the sound absorbing property superior in the tire can be expressed.
  • the second porous layer side is fixed to the tire side.
  • any appropriate means can be adopted depending on the use environment required for the tire. Examples of such means include an acrylic double-sided tape for tires that are less used in a low-temperature environment, and a rubber-type double-sided tape for tires that are frequently used in a low-temperature environment.
  • An acrylic double-sided tape having an acrylic pressure-sensitive adhesive layer for example, a base-less double-sided tape composed of an acrylic pressure-sensitive adhesive layer / separator).
  • the thickness of the acrylic double-sided tape as a means for fixing the sound-absorbing material of the present invention to the tire is preferably 360 ⁇ m or less, more preferably 260 ⁇ m or less, further preferably 160 ⁇ m or less, and particularly preferably 60 ⁇ m or less. is there.
  • the lower limit thickness is preferably 4 ⁇ m or more, more preferably 20 ⁇ m or more, still more preferably 30 ⁇ m or more, and particularly preferably 40 ⁇ m or more.
  • a test piece obtained by adhering it to a backing material is a temperature of 23 ° C. and a humidity of 50%.
  • the rubber plate butyl rubber
  • the test piece was peeled off from the rubber plate at a temperature of 100 ° C. and an angle of 180 degrees.
  • the adhesive strength when peeled at a peeling speed of 300 mm / min is preferably 0.1 N / 20 mm to 100 N / 20 mm, more preferably 0.3 N / 20 mm to 50 N / 20 mm, and even more preferably 0.5 N / 20 mm to 30 N / 20 mm, particularly preferably 0.7 N / 20 mm to 10 N / 20 mm, and most preferably 1 N / 20 mm to 5 N / It is 0mm.
  • the rubber-based double-sided tape as a means for fixing the sound-absorbing material of the present invention to a tire, for example, a pressure-sensitive adhesive composition containing a styrene-based elastomer (for example, SIS) and a crosslinking agent (for example, an isocyanate-based crosslinking agent).
  • a rubber-based double-sided tape having a rubber-based pressure-sensitive adhesive layer for example, a double-sided tape comprising a rubber-based pressure-sensitive adhesive layer / non-woven fabric / rubber-based pressure-sensitive adhesive layer / separator).
  • the upper limit thickness of the rubber-based double-sided tape as a means for fixing the sound-absorbing material of the present invention to the tire is preferably 360 ⁇ m or less, more preferably 290 ⁇ m or less, still more preferably 220 ⁇ m or less, and particularly preferably 150 ⁇ m. It is as follows.
  • the lower limit thickness is preferably 4 ⁇ m or more, more preferably 40 ⁇ m or more, still more preferably 80 ⁇ m or more, and particularly preferably 120 ⁇ m or more.
  • a test piece obtained by bonding it to a backing material is a temperature of 23 ° C. and a humidity of 50%.
  • the rubber plate butyl rubber
  • the test piece was peeled off from the rubber plate at a temperature of 100 ° C. and an angle of 180 degrees.
  • the adhesive strength when peeled at a peeling speed of 300 mm / min is preferably 0.1 N / 20 mm to 100 N / 20 mm, more preferably 0.3 N / 20 mm to 50 N / 20 mm, and even more preferably 0.5 N / 20 mm to 30 N / 20 mm, particularly preferably 0.7 N / 20 mm to 10 N / 20 mm, and most preferably 1 N / 20 mm to 5 N / 20 mm.
  • the first perforated layer has a plurality of through holes in the thickness direction.
  • any appropriate shape such as a perfect circle shape, an ellipse shape, a triangle shape, a square shape, a polygon shape, and a slit shape can be adopted.
  • a circular shape, an elliptical shape, and a quadrangular shape are preferable, and a circular shape is more preferable from the viewpoint that the effects of the present invention can be more manifested and that the manufacturing is easy.
  • the shape of the surface opening of the first perforated layer formed by the plurality of through holes of the first perforated layer may be only one type or two or more types.
  • the circle-equivalent hole diameter of the plurality of surface openings of the first perforated layer formed by the plurality of through holes of the first perforated layer is preferably 1 mm or more in that the effect of the present invention can be more manifested.
  • the thickness is more preferably 1 mm to 100 mm, further preferably 2 mm to 50 mm, further preferably 3 mm to 30 mm, still more preferably 4 mm to 20 mm, and particularly preferably 5 mm to 10 mm.
  • the circle-equivalent hole diameter of the surface opening is the diameter of a circle having the same area as the surface opening.
  • the surface opening ratio which is the ratio of the plurality of surface openings of the first perforated layer to the entire surface of the first perforated layer, is preferably 20% or less in that the effect of the present invention can be more expressed. More preferably, it is 0.01% to 20%, more preferably 0.05% to 10%, still more preferably 0.1% to 5%, still more preferably 0.2% to 4%. Particularly preferably 0.3% to 3%, most preferably 0.4% to 2%.
  • the surface opening ratio is defined as S total (mm 2 ) as the area of the entire surface (including the surface opening), and S open (mm 2 ) as the sum of the areas of the plurality of surface openings on the surface. Sopen / Stotal ) ⁇ 100 (%).
  • the thickness of the first perforated layer is less than 1 mm.
  • the thickness of the first perforated layer is preferably from 0.0001 mm to 0.9999 mm, more preferably from 0.0005 mm to 0.5 mm, and even more preferably from the viewpoint that the effects of the present invention can be more manifested.
  • 001 mm to 0.2 mm more preferably 0.001 mm to 0.1 mm, more preferably 0.001 mm to 0.05 mm, particularly preferably 0.002 mm to 0.03 mm, and most preferably 0.004 mm to 0.015 mm.
  • the areal density of the first perforation layer in that the effect of the present invention may be more expressed, preferably at 1000 g / m 2 or less, more preferably 0.05g / m 2 ⁇ 1000g / m 2, more preferably Is 0.5 g / m 2 to 500 g / m 2 , particularly preferably 0.5 g / m 2 to 200 g / m 2 , and most preferably 3 g / m 2 to 50 g / m 2 .
  • any appropriate material can be adopted as the material constituting the first perforated layer as long as the effects of the present invention are not impaired.
  • a material is preferably at least one selected from a resin, a metal, a rubber, an inorganic material, a woven fabric, and a non-woven fabric in that the effects of the present invention can be further expressed.
  • resins that can be the material constituting the first perforated layer include, for example, polyester resins (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), acrylic resins, polyolefin resins (polyethylene, polypropylene, etc.) , Polycarbonate resin, styrene resin, polyvinyl chloride, and the like.
  • resins that can be a material constituting the first perforated layer include aluminum, stainless steel (SUS), iron, copper, and the like.
  • the material constituting the first perforated layer is a resin
  • a layered shape such as a resin film (polyethylene terephthalate film, etc.), an adhesive tape, an adhesive tape or the like may be employed as it is, or a resin material capable of forming a coating film.
  • a resin layer formed by melting a porous layer as in a melt process may be employed.
  • the surface of the first perforated layer may be subjected to any appropriate surface treatment or surface processing as long as the effects of the present invention are not impaired.
  • the second perforated layer has a plurality of through holes in the thickness direction.
  • any appropriate shape such as a perfect circle shape, an ellipse shape, a triangle shape, a square shape, a polygon shape, and a slit shape can be adopted.
  • a circular shape, an elliptical shape, and a quadrangular shape are preferable, and a circular shape is more preferable from the viewpoint that the effects of the present invention can be more manifested and that the manufacturing is easy.
  • the shape of the surface opening of the second perforated layer formed by the plurality of through holes of the second perforated layer may be only one type or two or more types.
  • the circle equivalent hole diameter of the plurality of surface openings of the second perforated layer formed by the plurality of through holes of the second perforated layer is preferably 1 mm or more in that the effect of the present invention can be more expressed.
  • the thickness is more preferably 1 mm to 100 mm, further preferably 2 mm to 50 mm, further preferably 3 mm to 30 mm, still more preferably 4 mm to 20 mm, and particularly preferably 5 mm to 10 mm.
  • the circle-equivalent hole diameter of the surface opening is the diameter of a circle having the same area as the surface opening.
  • the surface opening ratio which is the ratio of the plurality of surface opening portions of the second perforated layer to the entire surface of the second perforated layer, is preferably 20% or less in that the effect of the present invention can be more expressed. More preferably, it is 0.01% to 20%, more preferably 0.05% to 10%, still more preferably 0.1% to 5%, still more preferably 0.2% to 4%. Particularly preferably 0.3% to 3%, most preferably 0.4% to 2%.
  • the surface opening ratio is defined as S total (mm 2 ) as the area of the entire surface (including the surface opening), and S open (mm 2 ) as the sum of the areas of the plurality of surface openings on the surface. Sopen / Stotal ) ⁇ 100 (%).
  • the thickness of the second perforated layer is preferably less than 1 mm, more preferably 0.0001 mm to 0.9999 mm, still more preferably 0.0005 mm to 0.5 mm, and still more preferably 0.001 mm to 0.00. 2 mm, more preferably 0.001 mm to 0.1 mm, further preferably 0.001 mm to 0.05 mm, particularly preferably 0.002 mm to 0.03 mm, and most preferably 0.004 mm to 0.015 mm.
  • the thickness of the second perforated layer is within the above range, it is possible to provide a sound absorbing material that is thinner and lighter and has excellent low frequency sound absorbing properties.
  • the areal density of the second perforation layer in that the effect of the present invention may be more expressed, preferably at 1000 g / m 2 or less, more preferably 0.05g / m 2 ⁇ 1000g / m 2, more preferably Is 0.5 g / m 2 to 500 g / m 2 , particularly preferably 0.5 g / m 2 to 200 g / m 2 , and most preferably 3 g / m 2 to 50 g / m 2 .
  • any appropriate material can be adopted as the material constituting the second perforated layer as long as the effects of the present invention are not impaired.
  • a material is preferably at least one selected from a resin, a metal, a rubber, an inorganic material, a woven fabric, and a non-woven fabric in that the effects of the present invention can be further expressed.
  • resins that can be the material constituting the second perforated layer include, for example, polyester resins (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), acrylic resins, polyolefin resins (polyethylene, polypropylene, etc.) , Polycarbonate resin, styrene resin, polyvinyl chloride, and the like.
  • resins that can be the material constituting the second perforated layer include, for example, polyester resins (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), acrylic resins, polyolefin resins (polyethylene, polypropylene, etc.) , Polycarbonate resin, styrene resin, polyvinyl chloride, and the like.
  • metal that can be a material constituting the second perforated layer include, for example, aluminum, stainless steel (SUS), iron, copper, and the like.
  • the material constituting the second perforated layer is a resin
  • a layered shape such as a resin film (polyethylene terephthalate film, etc.), an adhesive tape, an adhesive tape or the like may be used as it is, or a resin material capable of forming a coating film.
  • a resin layer formed by melting a porous layer as in a melt process may be employed.
  • the surface of the second perforated layer may be subjected to any appropriate surface treatment or surface processing as long as the effects of the present invention are not impaired.
  • the first porous layer has a plurality of voids (porous).
  • the structure of the porosity of the first porous layer is not particularly limited, but may be a structure in which at least a part of each void is three-dimensionally continuous (for example, an open cell structure).
  • the average equivalent hole diameter of the plurality of surface openings of the first porous layer formed by the porosity of the first porous layer is preferably the first perforation formed by the plurality of through holes of the first perforated layer. It is smaller than the equivalent circle diameter of the plurality of surface openings of the layer.
  • the average equivalent circular hole diameter of the plurality of surface opening portions of the first porous layer formed by the porosity of the first porous layer is preferably less than 5000 ⁇ m, more preferably in that the effect of the present invention can be more manifested. Is 1 ⁇ m to 5000 ⁇ m, more preferably 10 ⁇ m to 4000 ⁇ m, still more preferably 20 ⁇ m to 3000 ⁇ m, still more preferably 50 ⁇ m to 2000 ⁇ m, and particularly preferably 100 ⁇ m to 1000 ⁇ m.
  • the average equivalent hole diameter of the surface opening is the diameter of a circle having the same area as the surface opening.
  • the thickness of the first porous layer is preferably 1 mm or more, more preferably 2 mm to 200 mm, further preferably 3 mm to 100 mm, particularly preferably 4 mm to 50 mm, and most preferably 5 mm to 30 mm. .
  • the thickness of the first porous layer is within the above range, it is possible to provide a sound absorbing material that is thinner and lighter and has excellent low-frequency sound absorbing properties.
  • the density of the first porous layer is preferably 300 kg / m 3 or less, more preferably 1 kg / m 3 to 300 kg / m 3 , still more preferably 1 kg / m 3 to 200 kg / m 3 , and even more preferably. Is 1 kg / m 3 to 100 kg / m 3 , more preferably 5 kg / m 3 to 70 kg / m 3 , particularly preferably 5 kg / m 3 to 50 kg / m 3 , most preferably 10 kg / m 3. ⁇ 30 kg / m 3 . If the density of the first porous layer is within the above range, it is possible to provide a sound absorbing material that is lighter and has excellent low frequency sound absorbing properties.
  • the first porous layer has a plurality of holes formed with a length of D1 or less in the thickness direction from at least one surface of the first porous layer, where D1 is the thickness of the first porous layer. May be.
  • a hole for example, as shown in the schematic cross-sectional view of FIG. 5A, a plurality of holes 1b formed from one surface of the first porous layer 10B to the middle in the thickness direction, As shown in the schematic cross-sectional view of FIG. 5B, a plurality of hole portions 1b formed from one surface of the first porous layer 10B to the last (the other surface) in the thickness direction, and the like can be given.
  • the circle-equivalent hole diameter of the plurality of surface openings of the first porous layer formed by the plurality of holes that the first porous layer may have is preferably 1 mm or more in that the effect of the present invention can be more manifested. More preferably 1 mm to 100 mm, further preferably 2 mm to 50 mm, further preferably 3 mm to 30 mm, further preferably 4 mm to 20 mm, and particularly preferably 5 mm to 10 mm.
  • the circle-equivalent hole diameter of the surface opening is the diameter of a circle having the same area as the surface opening.
  • the surface opening ratio which is the ratio of the plurality of surface openings of the first porous layer formed by the plurality of pores that the first porous layer can have to the entire surface of the first porous layer, is an effect of the present invention. Is preferably 20% or less, more preferably 0.001% to 20%, still more preferably 0.01% to 10%, and still more preferably 0.1% to It is 5%, more preferably 0.2% to 4%, particularly preferably 0.3% to 3%, and most preferably 0.4% to 2%.
  • the surface opening ratio is defined as S total (mm 2 ) as the area of the entire surface (including the surface opening), and S open (mm 2 ) as the sum of the areas of the plurality of surface openings on the surface. Sopen / Stotal ) ⁇ 100 (%).
  • the plurality of surface openings of the first porous layer formed by the holes overlap with the plurality of surface openings of the first perforated layer in plan view. It may be arranged.
  • any of the plurality of hole portions of the first porous layer is disposed in the extending direction of each of the plurality of through holes of the first perforated layer on the first porous layer side. Is done.
  • the through hole extending from the surface of the first porous layer on the opposite side of the first porous layer to the surface of the first porous layer on the opposite side of the first porous layer.
  • any appropriate material can be adopted as the material constituting the first porous layer as long as the effects of the present invention are not impaired.
  • a material is preferably a polymer porous body, a metal porous body, an inorganic porous body, a woven cloth porous body, a non-woven cloth porous body, a fiber, in that the effect of the present invention can be expressed more. At least one selected from the group of materials and polymer monoliths.
  • polymer porous body that can be a material constituting the first porous layer
  • polyurethane foam for example, polystyrene foam, polyolefin (for example, polyethylene, polypropylene) foam, ethylene / propylene / diene rubber (EPDM) foam and the like.
  • EPDM ethylene / propylene / diene rubber
  • the porous structure of the polymer porous body any appropriate structure can be adopted depending on the purpose.
  • each of the bubbles formed by foaming may be an independent closed cell structure, or may be an open cell structure in which at least a part of the bubbles is continuous.
  • fibrous material that can be a material constituting the first porous layer include glass wool, rock wool, felt material, and the like.
  • polymer monolith body that can be a material constituting the first porous layer include, for example, a silicone monolith body as described in JP-A-2014-61457.
  • the second porous layer has a plurality of voids (porous).
  • the structure of the porosity of the second porous layer is not particularly limited, but may be a structure in which at least a part of each void is three-dimensionally continuous (for example, an open cell structure).
  • the average equivalent hole diameter of the plurality of surface openings of the second porous layer formed by the porosity of the second porous layer is preferably the second perforation formed by the plurality of through holes of the second perforated layer. It is smaller than the equivalent circle diameter of the plurality of surface openings of the layer.
  • the average equivalent circular pore diameter of the plurality of surface openings of the second porous layer formed by the porosity of the second porous layer is preferably less than 5000 ⁇ m, more preferably in that the effect of the present invention can be more manifested. Is 1 ⁇ m to 5000 ⁇ m, more preferably 10 ⁇ m to 4000 ⁇ m, still more preferably 20 ⁇ m to 3000 ⁇ m, still more preferably 50 ⁇ m to 2000 ⁇ m, and particularly preferably 100 ⁇ m to 1000 ⁇ m.
  • the average equivalent hole diameter of the surface opening is the diameter of a circle having the same area as the surface opening.
  • the thickness of the second porous layer is preferably 1 mm or more, more preferably 2 mm to 200 mm, further preferably 3 mm to 100 mm, particularly preferably 4 mm to 50 mm, and most preferably 5 mm to 30 mm. .
  • the thickness of the second porous layer is within the above range, it is possible to provide a sound absorbing material that is thinner and lighter and has excellent low frequency sound absorbing properties.
  • the density of the second porous layer is preferably 300 kg / m 3 or less, more preferably 1 kg / m 3 to 300 kg / m 3 , still more preferably 1 kg / m 3 to 200 kg / m 3 , and still more preferably. Is 1 kg / m 3 to 100 kg / m 3 , more preferably 5 kg / m 3 to 70 kg / m 3 , particularly preferably 5 kg / m 3 to 50 kg / m 3 , most preferably 10 kg / m 3. ⁇ 30 kg / m 3 . If the density of the second porous layer is within the above range, it is possible to provide a sound absorbing material that is lighter and has excellent low-frequency sound absorbing properties.
  • the second porous layer has a plurality of holes formed with a length of D2 or less in the thickness direction from at least one surface of the second porous layer, where D2 is the thickness of the second porous layer. May be.
  • a hole for example, as shown in the schematic cross-sectional view of FIG. 6A, a plurality of holes 2b formed from one surface of the second porous layer 20B to the middle in the thickness direction, As shown in the schematic cross-sectional view of FIG. 6B, there are a plurality of holes 2b formed from one surface of the second porous layer 20B to the last (the other surface) in the thickness direction.
  • the circle-equivalent hole diameter of the plurality of surface openings of the second porous layer formed by the plurality of holes that the second porous layer may have is preferably 1 mm or more in that the effect of the present invention can be more manifested. More preferably 1 mm to 100 mm, further preferably 2 mm to 50 mm, further preferably 3 mm to 30 mm, further preferably 4 mm to 20 mm, and particularly preferably 5 mm to 10 mm.
  • the circle-equivalent hole diameter of the surface opening is the diameter of a circle having the same area as the surface opening.
  • the surface opening ratio which is the ratio of the plurality of surface openings of the second porous layer formed by the plurality of pores that the second porous layer can have to the entire surface of the second porous layer, is an effect of the present invention. Is preferably 20% or less, more preferably 0.001% to 20%, still more preferably 0.01% to 10%, and still more preferably 0.1% to It is 5%, more preferably 0.2% to 4%, particularly preferably 0.3% to 3%, and most preferably 0.4% to 2%.
  • the surface opening ratio is defined as S total (mm 2 ) as the area of the entire surface (including the surface opening), and S open (mm 2 ) as the sum of the areas of the plurality of surface openings on the surface. Sopen / Stotal ) ⁇ 100 (%).
  • the plurality of surface openings of the second porous layer formed by the pores overlap with the plurality of surface openings of the second perforated layer in plan view. It may be arranged.
  • any of the plurality of hole portions of the second porous layer is disposed in the extending direction of each of the plurality of through holes of the second perforated layer on the second porous layer side. Is done.
  • the through hole extending from the surface of the second porous layer opposite to the second porous layer to the surface of the second porous layer opposite to the second porous layer.
  • any appropriate material can be adopted as the material constituting the second porous layer as long as the effects of the present invention are not impaired.
  • a material is preferably a polymer porous body, a metal porous body, an inorganic porous body, a woven cloth porous body, a non-woven cloth porous body, a fiber, in that the effect of the present invention can be expressed more. At least one selected from the group of materials and polymer monoliths.
  • polymer porous body that can be a material constituting the second porous layer
  • polyurethane foam for example, polystyrene foam, polyolefin (for example, polyethylene, polypropylene) foam, ethylene / propylene / diene rubber (EPDM) foam and the like.
  • EPDM ethylene / propylene / diene rubber
  • the porous structure of the polymer porous body any appropriate structure can be adopted depending on the purpose.
  • each of the bubbles formed by foaming may be an independent closed cell structure, or may be an open cell structure in which at least a part of the bubbles is continuous.
  • fibrous material that can be a material constituting the second porous layer include glass wool, rock wool, felt material, and the like.
  • polymer monolith body that can be a material constituting the second porous layer include, for example, a silicone monolith body as described in JP-A-2014-61457.
  • silicone grease Shin-Etsu Chemical G501
  • Example 2 The same procedure as in Example 1 was carried out except that the surface opening ratio by the through holes provided in the first perforated layer and the second perforated layer was changed to 0.5%, and [first perforated layer] / [acrylic double-sided adhesive tape] A sound-absorbing material (2) having a structure of / [urethane foam (first porous layer)] / [second perforated layer] / [urethane foam (second porous layer)] was obtained. The results are shown in FIG.
  • Example 3 The same procedure as in Example 1 was carried out except that the surface opening ratio by the through holes provided in the first perforated layer and the second perforated layer was changed to 0.75%, and [first perforated layer] / [acrylic double-sided adhesive tape] A sound-absorbing material (3) having a structure of / [urethane foam (first porous layer)] / [second perforated layer] / [urethane foam (second porous layer)] was obtained. The results are shown in FIG.
  • Example 4 Except for changing the surface aperture ratio of the through holes provided in the first perforated layer and the second perforated layer to 1.0%, the same procedure as in Example 1 was carried out, and [first perforated layer] / [acrylic double-sided adhesive tape] A sound-absorbing material (4) having a structure of / [urethane foam (first porous layer)] / [second perforated layer] / [urethane foam (second porous layer)] was obtained. The results are shown in FIG.
  • An acrylic double-sided adhesive tape (thickness 150 ⁇ m, manufactured by Nitto Denko Corporation, product name: No.
  • the first perforated layer has a plurality of through holes extending from the surface on the opposite side of the first porous layer to the surface on the opposite side of the second porous layer of the second porous layer.
  • a sound absorbing material (5) having a configuration of [acrylic double-sided adhesive tape] / [urethane foam (first porous layer)] / [second perforated layer] / [urethane foam (second porous layer)] was obtained. The results are shown in FIG.
  • Example 6 The same procedure as in Example 5 was performed except that the surface opening ratio due to the through holes was changed to 0.5%, and the second perforated layer of the second porous layer was formed from the surface opposite to the first porous layer of the first perforated layer.
  • a sound-absorbing material (6) having a structure of 2 porous layers)] was obtained. The results are shown in FIG.
  • Example 7 The same procedure as in Example 5 was performed except that the surface aperture ratio due to the through holes was changed to 0.75%, and the second perforated layer of the second porous layer was formed from the surface of the first perforated layer on the opposite side of the first porous layer.
  • a sound-absorbing material (7) having a structure of 2 porous layers)] was obtained. The results are shown in FIG.
  • Example 8 The same procedure as in Example 5 was carried out except that the surface opening ratio by the through-hole was changed to 1.0%, and the second perforated layer of the second porous layer was formed from the surface opposite to the first porous layer of the first perforated layer.
  • a sound-absorbing material (8) having the structure of 2 porous layers)] was obtained. The results are shown in FIG.
  • the sound absorbing material of the present invention can be used as a sound absorbing material for tires, for example.

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Abstract

薄型軽量で低周波の吸音性に優れた吸音材を提供する。　本発明の吸音材は、第１穿孔層と第１多孔層と第２穿孔層と第２多孔層をこの順に含む積層構造を有する吸音材であって、該第１穿孔層が厚み方向に複数の貫通孔を有し、該第２穿孔層が厚み方向に複数の貫通孔を有し、該第１穿孔層の厚みが１ｍｍ未満である。

Description

吸音材
　本発明は、吸音材に関する。
　吸音材として、従来、グラスウールのような繊維系材料やウレタンフォームのような発泡材料が広く用いられている。しかし、これらのような材料は、低周波の吸音性が悪く、低周波で十分な吸音を得るためには厚みの大きい材料を用いる必要がある。
　限られた厚みの材料で低周波の吸音を行うためには、共鳴（共振）によって低周波の吸音効果を得ることが一般的である。
　共鳴（共振）によって低周波の吸音効果を得るためには、板や膜を用いる方法や、スリットや穿孔板を用いてヘルムホルツ共鳴器を構成する方法が挙げられ、特に、スリットや穿孔板を用いてヘルムホルツ共鳴器を構成する方法（特に、穿孔板と背後層の組み合わせ）がよく採用されている。しかし、穿孔板は、重量が大きいという問題や、形状自由度に制限があるという問題がある。
　発泡プラスチックのような多孔シートと貫通孔を有する緻密シートが交互に積層された吸音材が報告されている（特許文献１）。しかし、この吸音材においては、比較的厚い緻密シートを必要とするため、低周波の吸音性と軽量性を両立することは困難である。
特公平４－３７９９４号公報
　本発明の課題は、薄型軽量で低周波の吸音性に優れた吸音材を提供することにある。
　本発明の吸音材は、
　第１穿孔層と第１多孔層と第２穿孔層と第２多孔層をこの順に含む積層構造を有する吸音材であって、
　該第１穿孔層が厚み方向に複数の貫通孔を有し、
　該第２穿孔層が厚み方向に複数の貫通孔を有し、
　該第１穿孔層の厚みが１ｍｍ未満である。
　一つの実施形態としては、上記第１穿孔層が有する複数の貫通孔により形成される該第１穿孔層の複数の表面開口部の最大孔径が１ｍｍ以上である。
　一つの実施形態としては、上記第１穿孔層の表面全体に対する上記複数の表面開口部の占める割合である表面開口率が２０％以下である。
　一つの実施形態としては、上記第２穿孔層が有する複数の貫通孔により形成される該第２穿孔層の複数の表面開口部の最大孔径が１ｍｍ以上である。
　一つの実施形態としては、上記第２穿孔層の表面全体に対する上記複数の表面開口部の占める割合である表面開口率が２０％以下である。
　一つの実施形態としては、上記第２穿孔層の厚みが１ｍｍ未満である。
　一つの実施形態としては、上記第１多孔層の厚みが１ｍｍ以上である。
　一つの実施形態としては、上記第２多孔層の厚みが１ｍｍ以上である。
　一つの実施形態としては、本発明の吸音材において、全体の厚みが３００ｍｍ未満である。
　一つの実施形態としては、上記第１多孔層の厚みをＤ１としたとき、該第１多孔層が、該第１多孔層の少なくとも一方の表面から厚み方向に長さがＤ１以下で形成された複数の孔部を有し、該複数の孔部により形成される該第１多孔層の複数の表面開口部の最大孔径が１ｍｍ以上である。
　一つの実施形態としては、平面視において上記第１多孔層の複数の表面開口部と上記第１穿孔層の複数の表面開口部とが重なる位置に配設されている。
　一つの実施形態としては、上記第２多孔層の厚みをＤ２としたとき、該第２多孔層が、該第２多孔層の少なくとも一方の表面から厚み方向に長さがＤ２以下で形成された複数の孔部を有し、該複数の孔部により形成される該第２多孔層の複数の表面開口部の最大孔径が１ｍｍ以上である。
　一つの実施形態としては、平面視において上記第２多孔層の複数の表面開口部と上記第２穿孔層の複数の表面開口部とが重なる位置に配設されている。
　一つの実施形態としては、上記第１穿孔層の上記第１多孔層の反対側の表面から上記第２多孔層の上記第２穿孔層の反対側の表面に至る貫通孔を複数有する。
　一つの実施形態としては、上記第１穿孔層を構成する材料が、樹脂、金属、ゴム、無機物、織布、不織布から選ばれる少なくとも１種である。
　一つの実施形態としては、上記第２穿孔層を構成する材料が、樹脂、金属、ゴム、無機物、織布、不織布から選ばれる少なくとも１種である。
　一つの実施形態としては、上記第１多孔層を構成する材料が、高分子多孔質体、金属多孔質体、無機物多孔質体、織布多孔質体、不織布多孔質体、繊維状材料、高分子モノリス体から選ばれる少なくとも１種である。
　一つの実施形態としては、上記第２多孔層を構成する材料が、高分子多孔質体、金属多孔質体、無機物多孔質体、織布多孔質体、不織布多孔質体、繊維状材料、高分子モノリス体から選ばれる少なくとも１種である。
　本発明によれば、薄型軽量で低周波の吸音性に優れた吸音材を提供することができる。
本発明の吸音材の一つの実施形態を示す概略断面図である。 本発明の吸音材のより具体的な一つの実施形態を示す概略断面図である。 本発明の吸音材のより具体的な一つの実施形態を示す概略断面図である。 本発明の吸音材のいくつかの実施形態を示す斜視図である。 第１多孔層が孔部を有する場合のいくつかの実施形態を示す概略断面図である。 第２多孔層が孔部を有する場合のいくつかの実施形態を示す概略断面図である。 吸音材（１）～（４）の吸音率を示すグラフ図である。 吸音材（５）～（８）の吸音率を示すグラフ図である。 吸音材（Ｃ１）の吸音率を示すグラフ図である。 吸音材（Ｃ２）～（Ｃ５）の吸音率を示すグラフ図である。
　本発明において、「穿孔層」とは、層の厚み方向に貫通する孔（貫通孔）を有する層を意味する。本発明において、「多孔層」とは、複数の空隙（多孔）を有する層を意味する。
　本発明の吸音材は、第１穿孔層と第１多孔層と第２穿孔層と第２多孔層をこの順に含む積層構造を有する。本発明の吸音材は、第１穿孔層と第１多孔層と第２穿孔層と第２多孔層をこの順に含む積層構造を有していれば、任意の適切な他の層を含んでいてもよい。このような他の層は、例えば、１つ以上の貫通孔を有していてもよい。
　第１穿孔層、第１多孔層、第２穿孔層、第２多孔層は、それぞれ、１層のみからなる層であってもよいし、２層以上の積層体であってもよい。
　本発明の吸音材は、好ましくは、第１穿孔層と第１多孔層と第２穿孔層と第２多孔層をこの順に含む積層構造を有し、第１穿孔層が最外層となっている。
　図１は、本発明の吸音材の一つの実施形態を示す概略断面図である。図１において、本発明の吸音材１００は、第１穿孔層１０Ａと第１多孔層１０Ｂと第２穿孔層２０Ａと第２多孔層２０Ｂを有する。図１において、第１穿孔層１０Ａと第２多孔層２０Ｂが最外層となっている。なお、図１においては、第１穿孔層１０Ａおよび第２穿孔層２０Ａが有する貫通孔、第１多孔層１０Ｂおよび第２多孔層２０Ｂが有する多孔は図示せずに省略している。
　図２は、本発明の吸音材のより具体的な一つの実施形態を示す概略断面図である。図２において、本発明の吸音材１００は、第１穿孔層１０Ａと第１多孔層１０Ｂと第２穿孔層２０Ａと第２多孔層２０Ｂを有する。図２において、第１穿孔層１０Ａと第２多孔層２０Ｂが最外層となっている。図２において、第１穿孔層１０Ａは、厚み方向に複数の貫通孔１ａを有する。図２において、第２穿孔層２０Ａは、厚み方向に複数の貫通孔２ａを有する。第１多孔層１０Ｂおよび第２多孔層２０Ｂが有する多孔は図示せずに省略している。図２においては、貫通孔１ａと貫通孔２ａは平面視において全てが重なる位置に配設されているが、一部が重ならない位置に配設されていてもよいし、全てが重ならない位置に配設されていてもよい。
　図３は、本発明の吸音材のより具体的な一つの実施形態を示す概略断面図である。図３において、本発明の吸音材１００は、第１穿孔層１０Ａと第１多孔層１０Ｂと第２穿孔層２０Ａと第２多孔層２０Ｂを有する。図３において、第１穿孔層１０Ａと第２多孔層２０Ｂが最外層となっている。図３において、本発明の吸音材１００は、第１穿孔層１０Ａの第１多孔層１０Ｂの反対側の表面から第２多孔層２０Ｂの第２穿孔層２０Ａの反対側の表面に至る貫通孔３を複数有する。第１多孔層１０Ｂおよび第２多孔層２０Ｂが有する多孔は図示せずに省略している。
　本発明の吸音材は、全体の厚みが、好ましくは３００ｍｍ未満であり、より好ましくは１ｍｍ～２００ｍｍであり、さらに好ましくは３ｍｍ～１００ｍｍであり、特に好ましくは５ｍｍ～５０ｍｍである。本発明の吸音材の全体の厚みが上記範囲内にあれば、薄型の吸音材となり、薄型吸音材が求められる様々な目的に使用し得る。
　本発明の吸音材の平均密度は、好ましくは３００ｋｇ／ｍ３以下であり、より好ましくは１ｋｇ／ｍ３～２００ｋｇ／ｍ３であり、さらに好ましくは５ｋｇ／ｍ３～１５０ｋｇ／ｍ３であり、特に好ましくは１０ｋｇ／ｍ３～１００ｋｇ／ｍ３であり、最も好ましくは２０ｋｇ／ｍ３～５０ｋｇ／ｍ３である。本発明の吸音材の密度が上記範囲内にあれば、より軽量で低周波の吸音性に優れた吸音材を提供することができる。
　本発明の吸音材は、図４（ａ）の斜視図に示すように、第１穿孔層１０Ａが側面までは覆っていない実施形態であってもよいし、図４（ｂ）の斜視図に示すように、第１穿孔層１０Ａが側面の途中まで覆う実施形態であってもよいし、図４（ｃ）の斜視図に示すように、第１穿孔層１０Ａが側面全体を覆う実施形態であってもよいし、図４（ｄ）の斜視図に示すように、第１穿孔層１０Ａが側面全体および背面の一部を覆う実施形態であってもよいし、図４（ｅ）の斜視図に示すように、第１穿孔層１０Ａが側面全体および背面全体を覆う実施形態であってもよい。また、図４（ｂ）、図４（ｃ）、図４（ｄ）、図４（ｅ）に示す実施形態において、側面の少なくとも一部を覆う部分や背面の少なくとも一部を覆う部分が第１穿孔層１０Ａとは別の層である実施形態であってもよい。
　本発明の吸音材の長さ方向の端面の少なくとも一部は、本発明の効果を損なわない範囲で任意の適切な層によって塞がれていてもよい。また、本発明の吸音材の長さ方向の端面は、プレスなどによって断面形状が変形されて塞がれていてもよい。
　本発明の吸音材は、薄型軽量で低周波の吸音性に優れるため、各種の用途に採用可能である。本発明の吸音材は、低周波領域において非常に優れた吸音性を発現できるので、例えば、タイヤ用吸音材、特に空洞共鳴音対策として採用可能である。特に、本発明の吸音材をタイヤ用吸音材として採用する場合には、２００Ｈｚ～３００Ｈｚの領域において優れた吸音性を発現することが好ましい。本発明の吸音材をタイヤ用吸音材として用いる場合、タイヤにおけるより優れた吸音性を発現し得る点で、好ましくは、図４（ｂ）、図４（ｃ）、図４（ｄ）、図４（ｅ）に示す実施形態であり、より好ましくは、図４（ｃ）、図４（ｄ）、図４（ｅ）に示す実施形態である。
　本発明の吸音材をタイヤ用吸音材として用いる場合、第１穿孔層側と第２多孔層側のいずれがタイヤ側に設置されてもよく、タイヤにおけるより優れた吸音性を発現し得る点で、好ましくは、第２多孔層側がタイヤ側に固定される。本発明の吸音材をタイヤに固定する手段としては、タイヤに求められる使用環境によって任意の適切な手段が採用され得る。このような手段としては、例えば、低温環境での使用が少ないタイヤについては、アクリル系両面テープなどが挙げられ、低温環境での使用が多いタイヤについては、ゴム系両面テープなどが挙げられる。
　本発明の吸音材をタイヤに固定する手段としてのアクリル系両面テープとしては、例えば、（メタ）アクリル酸アルキルエステル（例えば、２－エチルヘキシルアクリレートなど）と（メタ）アクリル酸とエポキシ基含有（メタ）アクリレート（例えば、グルシジルメタクリレートなど）を含む単量体組成物を重合して得られる（メタ）アクリル系ポリマーと架橋剤（例えば、イソシアネート系架橋剤など）とを含む粘着剤組成物から形成されるアクリル系粘着剤層を有するアクリル系両面テープ（例えば、アクリル系粘着剤層／セパレーターの構成からなる基材レス両面テープなど）が挙げられる。
　本発明の吸音材をタイヤに固定する手段としてのアクリル系両面テープの厚みは、好ましくは３６０μｍ以下であり、より好ましくは２６０μｍ以下であり、さらに好ましくは１６０μｍ以下であり、特に好ましくは６０μｍ以下である。下限の厚みは、好ましくは４μｍ以上であり、より好ましくは２０μｍ以上であり、さらに好ましくは３０μｍ以上であり、特に好ましくは４０μｍ以上である。
　本発明の吸音材をタイヤに固定する手段としてのアクリル系両面テープが有するアクリル系粘着剤層において、それを裏打ち材（ＰＥＴ＃２５）に貼り合せた試験片を、温度２３℃、湿度５０％ＲＨにて、ゴム板（ブチルゴム）に２ｋｇローラーで一往復圧着させ、温度１００℃にて３０分間養生した後に、該ゴム板から該試験片を、温度１００℃にて、引き剥がし角度１８０度、引き剥がし速度３００ｍｍ／分で剥離したときの粘着力が、好ましくは０．１Ｎ／２０ｍｍ～１００Ｎ／２０ｍｍであり、より好ましくは０．３Ｎ／２０ｍｍ～５０Ｎ／２０ｍｍであり、さらに好ましくは０．５Ｎ／２０ｍｍ～３０Ｎ／２０ｍｍであり、特に好ましくは０．７Ｎ／２０ｍｍ～１０Ｎ／２０ｍｍであり、最も好ましくは１Ｎ／２０ｍｍ～５Ｎ／２０ｍｍである。
　本発明の吸音材をタイヤに固定する手段としてのゴム系両面テープとしては、例えば、スチレン系エラストマー（例えば、ＳＩＳなど）と架橋剤（例えば、イソシアネート系架橋剤など）とを含む粘着剤組成物から形成されるゴム系粘着剤層を有するゴム系両面テープ（例えば、ゴム系粘着剤層／不織布／ゴム系粘着剤層／セパレーターの構成からなる両面テープなど）が挙げられる。
　本発明の吸音材をタイヤに固定する手段としてのゴム系両面テープの上限の厚みは、好ましくは３６０μｍ以下であり、より好ましくは２９０μｍ以下であり、さらに好ましくは２２０μｍ以下であり、特に好ましくは１５０μｍ以下である。下限の厚みは、好ましくは４μｍ以上であり、より好ましくは４０μｍ以上であり、さらに好ましくは８０μｍ以上であり、特に好ましくは１２０μｍ以上である。
　本発明の吸音材をタイヤに固定する手段としてのゴム系両面テープが有するゴム系粘着剤層において、それを裏打ち材（ＰＥＴ＃２５）に貼り合せた試験片を、温度２３℃、湿度５０％ＲＨにて、ゴム板（ブチルゴム）に２ｋｇローラーで一往復圧着させ、温度１００℃にて３０分間養生した後に、該ゴム板から該試験片を、温度１００℃にて、引き剥がし角度１８０度、引き剥がし速度３００ｍｍ／分で剥離したときの粘着力が、好ましくは０．１Ｎ／２０ｍｍ～１００Ｎ／２０ｍｍであり、より好ましくは０．３Ｎ／２０ｍｍ～５０Ｎ／２０ｍｍであり、さらに好ましくは０．５Ｎ／２０ｍｍ～３０Ｎ／２０ｍｍであり、特に好ましくは０．７Ｎ／２０ｍｍ～１０Ｎ／２０ｍｍであり、最も好ましくは１Ｎ／２０ｍｍ～５Ｎ／２０ｍｍである。
＜第１穿孔層＞
　第１穿孔層は厚み方向に複数の貫通孔を有する。貫通孔により形成される第１穿孔層の表面開口部の形状としては、正円型、楕円型、三角型、四角型、多角型、スリット型など、任意の適切な形状を採用し得る。このような形状の中でも、本発明の効果がより発現され得る点や、製造し易い点から、正円型、楕円形、四角形が好ましく、正円型がより好ましい。第１穿孔層が有する複数の貫通孔により形成される第１穿孔層の表面開口部の形状は、１種のみであってもよいし、２種以上であってもよい。
　第１穿孔層が有する複数の貫通孔により形成される該第１穿孔層の複数の表面開口部の円相当孔径は、本発明の効果がより発現され得る点で、好ましくは１ｍｍ以上であり、より好ましくは１ｍｍ～１００ｍｍであり、さらに好ましくは２ｍｍ～５０ｍｍであり、さらに好ましくは３ｍｍ～３０ｍｍであり、さらに好ましくは４ｍｍ～２０ｍｍであり、特に好ましくは５ｍｍ～１０ｍｍである。表面開口部の円相当孔径とは、表面開口部と同じ面積を持つ円の直径である。
　第１穿孔層の表面全体に対する、第１穿孔層が有する複数の表面開口部の占める割合である表面開口率は、本発明の効果がより発現され得る点で、好ましくは２０％以下であり、より好ましくは０．０１％～２０％であり、さらに好ましくは０．０５％～１０％であり、さらに好ましくは０．１％～５％であり、さらに好ましくは０．２％～４％であり、特に好ましくは０．３％～３％であり、最も好ましくは０．４％～２％である。表面開口率は、表面全体の面積（表面開口部も含む）をＳｔｏｔａｌ（ｍｍ２）、該表面が有する複数の表面開口部の面積の合計をＳｏｐｅｎ（ｍｍ２）としたときに、（Ｓｏｐｅｎ／Ｓｔｏｔａｌ）×１００（％）である。
　第１穿孔層の厚みは１ｍｍ未満である。第１穿孔層の厚みが１ｍｍ未満であることにより、本発明の他の特徴と相まって、薄型軽量で低周波の吸音性に優れた吸音材を提供し得る。第１穿孔層の厚みは、本発明の効果がより発現され得る点で、好ましくは０．０００１ｍｍ～０．９９９９ｍｍであり、より好ましくは０．０００５ｍｍ～０．５ｍｍであり、さらに好ましくは０．００１ｍｍ～０．２ｍｍであり、さらに好ましくは０．００１ｍｍ～０．１ｍｍであり、さらに好ましくは０．００１ｍｍ～０．０５ｍｍであり、特に好ましくは０．００２ｍｍ～０．０３ｍｍであり、最も好ましくは０．００４ｍｍ～０．０１５ｍｍである。
　第１穿孔層の面密度は、本発明の効果がより発現され得る点で、好ましくは１０００ｇ／ｍ２以下であり、より好ましくは０．０５ｇ／ｍ２～１０００ｇ／ｍ２であり、さらに好ましくは０．５ｇ／ｍ２～５００ｇ／ｍ２であり、特に好ましくは０．５ｇ／ｍ２～２００ｇ／ｍ２であり、最も好ましくは３ｇ／ｍ２～５０ｇ／ｍ２である。
　第１穿孔層を構成する材料は、本発明の効果を損なわない範囲で任意の適切な材料を採用し得る。このような材料としては、本発明の効果がより発現され得る点で、好ましくは、樹脂、金属、ゴム、無機物、織布、不織布から選ばれる少なくとも１種である。第１穿孔層を構成する材料となり得る樹脂の具体的な例としては、例えば、ポリエステル樹脂（ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレートなど）、アクリル系樹脂、ポリオレフィン系樹脂（ポリエチレン、ポリプロピレンなど）、ポリカーボネート系樹脂、スチレン系樹脂、ポリ塩化ビニル、などが挙げられる。第１穿孔層を構成する材料となり得る金属の具体的な例としては、例えば、アルミニウム、ステンレス（ＳＵＳ）、鉄、銅などが挙げられる。第１穿孔層を構成する材料が樹脂の場合、樹脂フィルム（ポリエチレンテレフタレートフィルムなど）、接着テープ、粘着テープなどの層状形状のものをそのまま採用してもよいし、塗膜を形成しうる樹脂材料を塗装して形成された樹脂層を採用してもよい。また、例えばメルトーム加工のように多孔層を溶融して形成された樹脂層を採用してもよい。
　第１穿孔層の表面には、本発明の効果を損なわない範囲で任意の適切な表面処理や表面加工を行ってもよい。
＜第２穿孔層＞
　第２穿孔層は厚み方向に複数の貫通孔を有する。貫通孔により形成される第１穿孔層の表面開口部の形状としては、正円型、楕円型、三角型、四角型、多角型、スリット型など、任意の適切な形状を採用し得る。このような形状の中でも、本発明の効果がより発現され得る点や、製造し易い点から、正円型、楕円形、四角形が好ましく、正円型がより好ましい。第２穿孔層が有する複数の貫通孔により形成される第２穿孔層の表面開口部の形状は、１種のみであってもよいし、２種以上であってもよい。
　第２穿孔層が有する複数の貫通孔により形成される該第２穿孔層の複数の表面開口部の円相当孔径は、本発明の効果がより発現され得る点で、好ましくは１ｍｍ以上であり、より好ましくは１ｍｍ～１００ｍｍであり、さらに好ましくは２ｍｍ～５０ｍｍであり、さらに好ましくは３ｍｍ～３０ｍｍであり、さらに好ましくは４ｍｍ～２０ｍｍであり、特に好ましくは５ｍｍ～１０ｍｍである。表面開口部の円相当孔径とは、表面開口部と同じ面積を持つ円の直径である。
　第２穿孔層の表面全体に対する、第２穿孔層が有する複数の表面開口部の占める割合である表面開口率は、本発明の効果がより発現され得る点で、好ましくは２０％以下であり、より好ましくは０．０１％～２０％であり、さらに好ましくは０．０５％～１０％であり、さらに好ましくは０．１％～５％であり、さらに好ましくは０．２％～４％であり、特に好ましくは０．３％～３％であり、最も好ましくは０．４％～２％である。表面開口率は、表面全体の面積（表面開口部も含む）をＳｔｏｔａｌ（ｍｍ２）、該表面が有する複数の表面開口部の面積の合計をＳｏｐｅｎ（ｍｍ２）としたときに、（Ｓｏｐｅｎ／Ｓｔｏｔａｌ）×１００（％）である。
　第２穿孔層の厚みは、好ましくは１ｍｍ未満であり、より好ましくは０．０００１ｍｍ～０．９９９９ｍｍであり、さらに好ましくは０．０００５ｍｍ～０．５ｍｍであり、さらに好ましくは０．００１ｍｍ～０．２ｍｍであり、さらに好ましくは０．００１ｍｍ～０．１ｍｍであり、さらに好ましくは０．００１ｍｍ～０．０５ｍｍであり、特に好ましくは０．００２ｍｍ～０．０３ｍｍであり、最も好ましくは０．００４ｍｍ～０．０１５ｍｍである。第２穿孔層の厚みが上記範囲内にあることにより、より薄型軽量で低周波の吸音性に優れた吸音材を提供することができる。
　第２穿孔層の面密度は、本発明の効果がより発現され得る点で、好ましくは１０００ｇ／ｍ２以下であり、より好ましくは０．０５ｇ／ｍ２～１０００ｇ／ｍ２であり、さらに好ましくは０．５ｇ／ｍ２～５００ｇ／ｍ２であり、特に好ましくは０．５ｇ／ｍ２～２００ｇ／ｍ２であり、最も好ましくは３ｇ／ｍ２～５０ｇ／ｍ２である。
　第２穿孔層を構成する材料は、本発明の効果を損なわない範囲で任意の適切な材料を採用し得る。このような材料としては、本発明の効果がより発現され得る点で、好ましくは、樹脂、金属、ゴム、無機物、織布、不織布から選ばれる少なくとも１種である。第２穿孔層を構成する材料となり得る樹脂の具体的な例としては、例えば、ポリエステル樹脂（ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレートなど）、アクリル系樹脂、ポリオレフィン系樹脂（ポリエチレン、ポリプロピレンなど）、ポリカーボネート系樹脂、スチレン系樹脂、ポリ塩化ビニル、などが挙げられる。第２穿孔層を構成する材料となり得る金属の具体的な例としては、例えば、アルミニウム、ステンレス（ＳＵＳ）、鉄、銅などが挙げられる。第２穿孔層を構成する材料が樹脂の場合、樹脂フィルム（ポリエチレンテレフタレートフィルムなど）、接着テープ、粘着テープなどの層状形状のものをそのまま採用してもよいし、塗膜を形成しうる樹脂材料を塗装して形成された樹脂層を採用してもよい。また、例えばメルトーム加工のように多孔層を溶融して形成された樹脂層を採用してもよい。
　第２穿孔層の表面には、本発明の効果を損なわない範囲で任意の適切な表面処理や表面加工を行ってもよい。
＜第１多孔層＞
　第１多孔層は、複数の空隙（多孔）を有する。第１多孔層が有する多孔は、構造について特に制限はないが、それぞれの空隙の少なくとも一部が三次元的に連続する構造（例えば、連続気泡構造）であってもよい。
　第１多孔層が有する多孔により形成される該第１多孔層の複数の表面開口部の平均円相当孔径は、好ましくは、第１穿孔層が有する複数の貫通孔により形成される該第１穿孔層の複数の表面開口部の円相当孔径よりも小さい。
　第１多孔層が有する多孔により形成される該第１多孔層の複数の表面開口部の平均円相当孔径は、本発明の効果がより発現され得る点で、好ましくは５０００μｍ未満であり、より好ましくは１μｍ～５０００μｍであり、さらに好ましくは１０μｍ～４０００μｍであり、さらに好ましくは２０μｍ～３０００μｍであり、さらに好ましくは５０μｍ～２０００μｍであり、特に好ましくは１００μｍ～１０００μｍである。表面開口部の平均円相当孔径とは、表面開口部と同じ面積を持つ円の直径である。
　第１多孔層の厚みは、好ましくは１ｍｍ以上であり、より好ましくは２ｍｍ～２００ｍｍであり、さらに好ましくは３ｍｍ～１００ｍｍであり、特に好ましくは４ｍｍ～５０ｍｍであり、最も好ましくは５ｍｍ～３０ｍｍである。第１多孔層の厚みが上記範囲内にあることにより、より薄型軽量で低周波の吸音性に優れた吸音材を提供することができる。
　第１多孔層の密度は、好ましくは３００ｋｇ／ｍ３以下であり、より好ましくは１ｋｇ／ｍ３～３００ｋｇ／ｍ３であり、さらに好ましくは１ｋｇ／ｍ３～２００ｋｇ／ｍ３であり、さらに好ましくは１ｋｇ／ｍ３～１００ｋｇ／ｍ３であり、さらに好ましくは５ｋｇ／ｍ３～７０ｋｇ／ｍ３であり、特に好ましくは５ｋｇ／ｍ３～５０ｋｇ／ｍ３であり、最も好ましくは１０ｋｇ／ｍ３～３０ｋｇ／ｍ３である。第１多孔層の密度が上記範囲内にあれば、より軽量で低周波の吸音性に優れた吸音材を提供することができる。
　第１多孔層は、該第１多孔層の厚みをＤ１としたとき、該第１多孔層の少なくとも一方の表面から厚み方向に長さがＤ１以下で形成された複数の孔部を有していてもよい。このような孔部としては、例えば、図５（ａ）の概略断面図に示すように、第１多孔層１０Ｂの一方の表面から厚み方向の途中までに形成された複数の孔部１ｂや、図５（ｂ）の概略断面図に示すように、第１多孔層１０Ｂの一方の表面から厚み方向の最後（もう一方の表面）までに形成された複数の孔部１ｂなどが挙げられる。
　第１多孔層が有し得る複数の孔部により形成される該第１多孔層の複数の表面開口部の円相当孔径は、本発明の効果がより発現され得る点で、好ましくは１ｍｍ以上であり、より好ましくは１ｍｍ～１００ｍｍであり、さらに好ましくは２ｍｍ～５０ｍｍであり、さらに好ましくは３ｍｍ～３０ｍｍであり、さらに好ましくは４ｍｍ～２０ｍｍであり、特に好ましくは５ｍｍ～１０ｍｍである。表面開口部の円相当孔径とは、表面開口部と同じ面積を持つ円の直径である。
　第１多孔層の表面全体に対する、第１多孔層が有し得る複数の孔部により形成される該第１多孔層の複数の表面開口部の占める割合である表面開口率は、本発明の効果がより発現され得る点で、好ましくは２０％以下であり、より好ましくは０．００１％～２０％であり、さらに好ましくは０．０１％～１０％であり、さらに好ましくは０．１％～５％であり、さらに好ましくは０．２％～４％であり、特に好ましくは０．３％～３％であり、最も好ましくは０．４％～２％である。表面開口率は、表面全体の面積（表面開口部も含む）をＳｔｏｔａｌ（ｍｍ２）、該表面が有する複数の表面開口部の面積の合計をＳｏｐｅｎ（ｍｍ２）としたときに、（Ｓｏｐｅｎ／Ｓｔｏｔａｌ）×１００（％）である。
　第１多孔層が複数の孔部を有する場合、該孔部により形成される第１多孔層の複数の表面開口部は、平面視において、第１穿孔層の複数の表面開口部と重なる位置に配設されていてもよい。このような実施形態においては、好ましくは、第１穿孔層が有する複数の貫通孔のそれぞれの第１多孔層側の延長方向に、第１多孔層が有する複数の孔部のいずれかが配設される。このような実施形態としては、例えば、本発明の吸音材において、第１穿孔層の第１多孔層の反対側の表面から第１多孔層の第１穿孔層の反対側の表面に至る貫通孔を複数有する実施形態が挙げられる。
　第１多孔層を構成する材料は、本発明の効果を損なわない範囲で任意の適切な材料を採用し得る。このような材料としては、本発明の効果がより発現され得る点で、好ましくは、高分子多孔質体、金属多孔質体、無機物多孔質体、織布多孔質体、不織布多孔質体、繊維状材料、高分子モノリス体から選ばれる少なくとも１種である。第１多孔層を構成する材料となり得る高分子多孔質体の具体的な例としては、例えば、ポリウレタン発泡体、ポリスチレン発泡体、ポリオレフィン（例えば、ポリエチレン、ポリプロピレン）発泡体、エチレン・プロピレン・ジエンゴム（ＥＰＤＭ）発泡体などが挙げられる。高分子多孔質体の多孔質構造としては、目的に応じて任意の適切な構造が採用され得る。このような構造としては、例えば、発泡により形成されたそれぞれの気泡が独立した独立気泡構造であってもよいし、気泡の少なくとも一部が連続する連続気泡構造であってもよい。第１多孔層を構成する材料となり得る繊維状材料の具体的な例としては、例えば、グラスウール、ロックウール、フェルト材などが挙げられる。第１多孔層を構成する材料となり得る高分子モノリス体の具体的な例としては、例えば、特開２０１４－６１４５７号公報に記載のようなシリコーン製モノリス体などが挙げられる。
＜第２多孔層＞
　第２多孔層は、複数の空隙（多孔）を有する。第２多孔層が有する多孔は、構造について特に制限はないが、それぞれの空隙の少なくとも一部が三次元的に連続する構造（例えば、連続気泡構造）であってもよい。
　第２多孔層が有する多孔により形成される該第２多孔層の複数の表面開口部の平均円相当孔径は、好ましくは、第２穿孔層が有する複数の貫通孔により形成される該第２穿孔層の複数の表面開口部の円相当孔径よりも小さい。
　第２多孔層が有する多孔により形成される該第２多孔層の複数の表面開口部の平均円相当孔径は、本発明の効果がより発現され得る点で、好ましくは５０００μｍ未満であり、より好ましくは１μｍ～５０００μｍであり、さらに好ましくは１０μｍ～４０００μｍであり、さらに好ましくは２０μｍ～３０００μｍであり、さらに好ましくは５０μｍ～２０００μｍであり、特に好ましくは１００μｍ～１０００μｍである。表面開口部の平均円相当孔径とは、表面開口部と同じ面積を持つ円の直径である。
　第２多孔層の厚みは、好ましくは１ｍｍ以上であり、より好ましくは２ｍｍ～２００ｍｍであり、さらに好ましくは３ｍｍ～１００ｍｍであり、特に好ましくは４ｍｍ～５０ｍｍであり、最も好ましくは５ｍｍ～３０ｍｍである。第２多孔層の厚みが上記範囲内にあることにより、より薄型軽量で低周波の吸音性に優れた吸音材を提供することができる。
　第２多孔層の密度は、好ましくは３００ｋｇ／ｍ３以下であり、より好ましくは１ｋｇ／ｍ３～３００ｋｇ／ｍ３であり、さらに好ましくは１ｋｇ／ｍ３～２００ｋｇ／ｍ３であり、さらに好ましくは１ｋｇ／ｍ３～１００ｋｇ／ｍ３であり、さらに好ましくは５ｋｇ／ｍ３～７０ｋｇ／ｍ３であり、特に好ましくは５ｋｇ／ｍ３～５０ｋｇ／ｍ３であり、最も好ましくは１０ｋｇ／ｍ３～３０ｋｇ／ｍ３である。第２多孔層の密度が上記範囲内にあれば、より軽量で低周波の吸音性に優れた吸音材を提供することができる。
　第２多孔層は、該第２多孔層の厚みをＤ２としたとき、該第２多孔層の少なくとも一方の表面から厚み方向に長さがＤ２以下で形成された複数の孔部を有していてもよい。このような孔部としては、例えば、図６（ａ）の概略断面図に示すように、第２多孔層２０Ｂの一方の表面から厚み方向の途中までに形成された複数の孔部２ｂや、図６（ｂ）の概略断面図に示すように、第２多孔層２０Ｂの一方の表面から厚み方向の最後（もう一方の表面）までに形成された複数の孔部２ｂなどが挙げられる。
　第２多孔層が有し得る複数の孔部により形成される該第２多孔層の複数の表面開口部の円相当孔径は、本発明の効果がより発現され得る点で、好ましくは１ｍｍ以上であり、より好ましくは１ｍｍ～１００ｍｍであり、さらに好ましくは２ｍｍ～５０ｍｍであり、さらに好ましくは３ｍｍ～３０ｍｍであり、さらに好ましくは４ｍｍ～２０ｍｍであり、特に好ましくは５ｍｍ～１０ｍｍである。表面開口部の円相当孔径とは、表面開口部と同じ面積を持つ円の直径である。
　第２多孔層の表面全体に対する、第２多孔層が有し得る複数の孔部により形成される該第２多孔層の複数の表面開口部の占める割合である表面開口率は、本発明の効果がより発現され得る点で、好ましくは２０％以下であり、より好ましくは０．００１％～２０％であり、さらに好ましくは０．０１％～１０％であり、さらに好ましくは０．１％～５％であり、さらに好ましくは０．２％～４％であり、特に好ましくは０．３％～３％であり、最も好ましくは０．４％～２％である。表面開口率は、表面全体の面積（表面開口部も含む）をＳｔｏｔａｌ（ｍｍ２）、該表面が有する複数の表面開口部の面積の合計をＳｏｐｅｎ（ｍｍ２）としたときに、（Ｓｏｐｅｎ／Ｓｔｏｔａｌ）×１００（％）である。
　第２多孔層が複数の孔部を有する場合、該孔部により形成される第２多孔層の複数の表面開口部は、平面視において、第２穿孔層の複数の表面開口部と重なる位置に配設されていてもよい。このような実施形態においては、好ましくは、第２穿孔層が有する複数の貫通孔のそれぞれの第２多孔層側の延長方向に、第２多孔層が有する複数の孔部のいずれかが配設される。このような実施形態としては、例えば、本発明の吸音材において、第２穿孔層の第２多孔層の反対側の表面から第２多孔層の第２穿孔層の反対側の表面に至る貫通孔を複数有する実施形態が挙げられる。
　第２多孔層を構成する材料は、本発明の効果を損なわない範囲で任意の適切な材料を採用し得る。このような材料としては、本発明の効果がより発現され得る点で、好ましくは、高分子多孔質体、金属多孔質体、無機物多孔質体、織布多孔質体、不織布多孔質体、繊維状材料、高分子モノリス体から選ばれる少なくとも１種である。第２多孔層を構成する材料となり得る高分子多孔質体の具体的な例としては、例えば、ポリウレタン発泡体、ポリスチレン発泡体、ポリオレフィン（例えば、ポリエチレン、ポリプロピレン）発泡体、エチレン・プロピレン・ジエンゴム（ＥＰＤＭ）発泡体などが挙げられる。高分子多孔質体の多孔質構造としては、目的に応じて任意の適切な構造が採用され得る。このような構造としては、例えば、発泡により形成されたそれぞれの気泡が独立した独立気泡構造であってもよいし、気泡の少なくとも一部が連続する連続気泡構造であってもよい。第２多孔層を構成する材料となり得る繊維状材料の具体的な例としては、例えば、グラスウール、ロックウール、フェルト材などが挙げられる。第２多孔層を構成する材料となり得る高分子モノリス体の具体的な例としては、例えば、特開２０１４－６１４５７号公報に記載のようなシリコーン製モノリス体などが挙げられる。
　以下、実施例により本発明を具体的に説明するが、本発明はこれら実施例になんら限定されるものではない。なお、特に明記しない限り、実施例における部および％は質量基準である。
＜吸音率の測定＞
　吸音率は、音響管を用いた垂直入射吸音率として測定した。
　具体的には、Ｂｒｕｅｌ＆Ｋｊａｅｒ製４２０６の太管を用い、Φ１００ｍｍのサンプルを作製し、ＪＩＳ　Ａ　１４０５－２に準拠して測定した。ただし、サンプルは、曲げ振動の影響が出ないように、背面全面を音響管の壁面にアクリル系両面接着テープ（厚み＝１５０μｍ、日東電工株式会社製、製品名：Ｎｏ．５１２）で貼り付けて測定した。
　また、断面の影響が出ないように、隙間はシリコーングリース（信越化学工業　Ｇ５０１）を充填して測定した。
〔実施例１〕
　ポリエチレンテレフタレートフィルム（厚み＝４．８μｍ、東レ製、製品名：ルミラー）にφ５ｍｍの貫通孔を表面開口率０．２５％で設け、第１穿孔層とした。
　第１穿孔層に対して、ウレタンフォーム（厚み＝１０ｍｍ、株式会社イノアックコーポレーション製、製品名：カームフレックスＦ２）を貼り合せた。貼り合せには、アクリル系両面接着テープ（厚み＝５０μｍ、日東電工株式会社製、製品名：ＧＡ５９０５）を用いた。
　さらに、得られた積層物のウレタンフォーム側に、ウレタンフォーム（厚み＝１０ｍｍ、株式会社イノアックコーポレーション製、製品名：カームフレックスＦ２）をさらに貼り合せた。貼り合せには、アクリル系両面接着テープ（厚み＝１５０μｍ、日東電工株式会社製、製品名：Ｎｏ．５１２）にφ５ｍｍの貫通孔を表面開口率０．２５％で設けたもの（第２穿孔層）を用いた。
　以上のようにして、〔第１穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム（第１多孔層）〕／〔第２穿孔層〕／〔ウレタンフォーム（第２多孔層）〕の構成を有する吸音材（１）を得た。
　結果を図７に示した。
〔実施例２〕
　第１穿孔層および第２穿孔層に設ける貫通孔による表面開口率を０．５％に変更した以外は、実施例１と同様に行い、〔第１穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム（第１多孔層）〕／〔第２穿孔層〕／〔ウレタンフォーム（第２多孔層）〕の構成を有する吸音材（２）を得た。
　結果を図７に示した。
〔実施例３〕
　第１穿孔層および第２穿孔層に設ける貫通孔による表面開口率を０．７５％に変更した以外は、実施例１と同様に行い、〔第１穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム（第１多孔層）〕／〔第２穿孔層〕／〔ウレタンフォーム（第２多孔層）〕の構成を有する吸音材（３）を得た。
　結果を図７に示した。
〔実施例４〕
　第１穿孔層および第２穿孔層に設ける貫通孔による表面開口率を１．０％に変更した以外は、実施例１と同様に行い、〔第１穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム（第１多孔層）〕／〔第２穿孔層〕／〔ウレタンフォーム（第２多孔層）〕の構成を有する吸音材（４）を得た。
　結果を図７に示した。
〔実施例５〕
　ポリエチレンテレフタレートフィルム（厚み＝４．８μｍ、東レ製、製品名：ルミラー）に対して、ウレタンフォーム（厚み＝１０ｍｍ、株式会社イノアックコーポレーション製、製品名：カームフレックスＦ２）を貼り合せた。貼り合せには、アクリル系両面接着テープ（厚み＝５０μｍ、日東電工株式会社製、製品名：ＧＡ５９０５）を用いた。
　さらに、得られた積層物のウレタンフォーム側に、ウレタンフォーム（厚み＝１０ｍｍ、株式会社イノアックコーポレーション製、製品名：カームフレックスＦ２）をさらに貼り合せた。貼り合せには、アクリル系両面接着テープ（厚み＝１５０μｍ、日東電工株式会社製、製品名：Ｎｏ．５１２）を用いた。
　得られた積層体に対して、φ５ｍｍの貫通孔を表面開口率０．２５％で設けた。
　以上のようにして、第１穿孔層の第１多孔層の反対側の表面から第２多孔層の第２穿孔層の反対側の表面に至る貫通孔を複数有する、〔第１穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム（第１多孔層）〕／〔第２穿孔層〕／〔ウレタンフォーム（第２多孔層）〕の構成を有する吸音材（５）を得た。
　結果を図８に示した。
〔実施例６〕
　貫通孔による表面開口率を０．５％に変更した以外は、実施例５と同様に行い、第１穿孔層の第１多孔層の反対側の表面から第２多孔層の第２穿孔層の反対側の表面に至る貫通孔を複数有する、〔第１穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム（第１多孔層）〕／〔第２穿孔層〕／〔ウレタンフォーム（第２多孔層）〕の構成を有する吸音材（６）を得た。
　結果を図８に示した。
〔実施例７〕
　貫通孔による表面開口率を０．７５％に変更した以外は、実施例５と同様に行い、第１穿孔層の第１多孔層の反対側の表面から第２多孔層の第２穿孔層の反対側の表面に至る貫通孔を複数有する、〔第１穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム（第１多孔層）〕／〔第２穿孔層〕／〔ウレタンフォーム（第２多孔層）〕の構成を有する吸音材（７）を得た。
　結果を図８に示した。
〔実施例８〕
　貫通孔による表面開口率を１．０％に変更した以外は、実施例５と同様に行い、第１穿孔層の第１多孔層の反対側の表面から第２多孔層の第２穿孔層の反対側の表面に至る貫通孔を複数有する、〔第１穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム（第１多孔層）〕／〔第２穿孔層〕／〔ウレタンフォーム（第２多孔層）〕の構成を有する吸音材（８）を得た。
　結果を図８に示した。
〔比較例１〕
　ウレタンフォーム（厚み＝２０ｍｍ、株式会社イノアックコーポレーション製、製品名：カームフレックスＦ２）を、吸音材（Ｃ１）とした。
　結果を図９に示した。
〔比較例２〕
　ポリエチレンテレフタレートフィルム（厚み＝４．８μｍ、東レ製、製品名：ルミラー）にφ５ｍｍの貫通孔を表面開口率０．２５％で設け、穿孔層とした。
　穿孔層に対して、ウレタンフォーム（厚み＝２０ｍｍ、株式会社イノアックコーポレーション製、製品名：カームフレックスＦ２）を貼り合せた。貼り合せには、アクリル系両面接着テープ（厚み＝５０μｍ、日東電工株式会社製、製品名：ＧＡ５９０５）を用いた。
　以上のようにして、〔穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム〕の構成を有する吸音材（Ｃ２）を得た。
　結果を図１０に示した。
〔比較例３〕
　貫通孔による表面開口率を０．５％に変更した以外は、比較例２と同様に行い、〔穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム〕の構成を有する吸音材（Ｃ３）を得た。
　結果を図１０に示した。
〔比較例４〕
　貫通孔による表面開口率を０．７５％に変更した以外は、比較例２と同様に行い、〔穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム〕の構成を有する吸音材（Ｃ４）を得た。
　結果を図１０に示した。
〔比較例５〕
　貫通孔による表面開口率を１．０％に変更した以外は、比較例２と同様に行い、〔穿孔層〕／〔アクリル系両面接着テープ〕／〔ウレタンフォーム〕の構成を有する吸音材（Ｃ５）を得た。
　結果を図１０に示した。
　本発明の吸音材は、例えば、タイヤ用吸音材として利用できる。
１００　　吸音材
１０Ａ　　第１穿孔層
１０Ｂ　　第１多孔層
２０Ａ　　第２穿孔層
２０Ｂ　　第２多孔層
１ａ　　　貫通孔
２ａ　　　貫通孔
３　　　　貫通孔
１ｂ　　　孔部
２ｂ　　　孔部

Claims (18)

  1. 　第１穿孔層と第１多孔層と第２穿孔層と第２多孔層をこの順に含む積層構造を有する吸音材であって、
    　該第１穿孔層が厚み方向に複数の貫通孔を有し、
    　該第２穿孔層が厚み方向に複数の貫通孔を有し、
    　該第１穿孔層の厚みが１ｍｍ未満である、
    　吸音材。
  2. 　前記第１穿孔層が有する複数の貫通孔により形成される該第１穿孔層の複数の表面開口部の最大孔径が１ｍｍ以上である、請求項１に記載の吸音材。
  3. 　前記第１穿孔層の表面全体に対する前記複数の表面開口部の占める割合である表面開口率が２０％以下である、請求項２に記載の吸音材。
  4. 　前記第２穿孔層が有する複数の貫通孔により形成される該第２穿孔層の複数の表面開口部の最大孔径が１ｍｍ以上である、請求項１から３までのいずれかに記載の吸音材。
  5. 　前記第２穿孔層の表面全体に対する前記複数の表面開口部の占める割合である表面開口率が２０％以下である、請求項４に記載の吸音材。
  6. 　前記第２穿孔層の厚みが１ｍｍ未満である、請求項１から５までのいずれかに記載の吸音材。
  7. 　前記第１多孔層の厚みが１ｍｍ以上である、請求項１から６までのいずれかに記載の吸音材。
  8. 　前記第２多孔層の厚みが１ｍｍ以上である、請求項１から７までのいずれかに記載の吸音材。
  9. 　全体の厚みが３００ｍｍ未満である、請求項１から８までのいずれかに記載の吸音材。
  10. 　前記第１多孔層の厚みをＤ１としたとき、該第１多孔層が、該第１多孔層の少なくとも一方の表面から厚み方向に長さがＤ１以下で形成された複数の孔部を有し、該複数の孔部により形成される該第１多孔層の複数の表面開口部の最大孔径が１ｍｍ以上である、請求項１から９までのいずれかに記載の吸音材。
  11. 　平面視において前記第１多孔層の複数の表面開口部と前記第１穿孔層の複数の表面開口部とが重なる位置に配設されている、請求項１０に記載の吸音材。
  12. 　前記第２多孔層の厚みをＤ２としたとき、該第２多孔層が、該第２多孔層の少なくとも一方の表面から厚み方向に長さがＤ２以下で形成された複数の孔部を有し、該複数の孔部により形成される該第２多孔層の複数の表面開口部の最大孔径が１ｍｍ以上である、請求項１から１１までのいずれかに記載の吸音材。
  13. 　平面視において前記第２多孔層の複数の表面開口部と前記第２穿孔層の複数の表面開口部とが重なる位置に配設されている、請求項１２に記載の吸音材。
  14. 　前記第１穿孔層の前記第１多孔層の反対側の表面から前記第２多孔層の前記第２穿孔層の反対側の表面に至る貫通孔を複数有する、請求項１から１３までのいずれかに記載の吸音材。
  15. 　前記第１穿孔層を構成する材料が、樹脂、金属、ゴム、無機物、織布、不織布から選ばれる少なくとも１種である、請求項１から１４までのいずれかに記載の吸音材。
  16. 　前記第２穿孔層を構成する材料が、樹脂、金属、ゴム、無機物、織布、不織布から選ばれる少なくとも１種である、請求項１から１５までのいずれかに記載の吸音材。
  17. 　前記第１多孔層を構成する材料が、高分子多孔質体、金属多孔質体、無機物多孔質体、織布多孔質体、不織布多孔質体、繊維状材料、高分子モノリス体から選ばれる少なくとも１種である、請求項１から１６までのいずれかに記載の吸音材。
  18. 　前記第２多孔層を構成する材料が、高分子多孔質体、金属多孔質体、無機物多孔質体、織布多孔質体、不織布多孔質体、繊維状材料、高分子モノリス体から選ばれる少なくとも１種である、請求項１から１７までのいずれかに記載の吸音材。
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CN113692614A (zh) * 2019-04-18 2021-11-23 昭和电工材料株式会社 吸声材料
EP3958252A4 (en) * 2019-04-18 2022-06-08 Showa Denko Materials Co., Ltd. SOUND ABSORBING MATERIAL
CN110111763A (zh) * 2019-05-10 2019-08-09 华南理工大学 一种多层的穿孔声学超材料吸声结构
CN110395076A (zh) * 2019-09-03 2019-11-01 青岛森麒麟轮胎股份有限公司 可修补的静音轮胎
CN110395076B (zh) * 2019-09-03 2024-07-02 青岛森麒麟轮胎股份有限公司 可修补的静音轮胎

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EP3588487A4 (en) 2020-12-23
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