JP7328353B2 - Multi-layer sound absorbing material - Google Patents

Description

The present invention relates to multilayer sound absorbers. Specifically, a multilayer sound absorbing material in which a low-permeability resin layer, an air-permeability resin foam layer, an air layer, and a low-permeability resin layer are laminated in this order, or a layer containing a fiber assembly is placed in the air layer. It relates to a multilayer sound absorbing material further provided in

Resin foam materials are used as materials for replacing conventional solid resin materials and metal materials, as members of automobiles and electronic devices, and as structural materials for containers. These resin foam materials are characterized by low density, high heat insulation, and cushioning properties, and these properties are mainly used effectively. On the other hand, properties expected of resin foam materials include sound absorption and sound insulation, but the scope of their application has been limited in the past.

The reason for this is that sound absorption and sound insulation are not characteristics that are expressed in foams in general, but rather depend on the cell structure. The body has excellent rigidity and mechanical strength, but its sound absorption and sound insulation performance is very low. Each property tends to contradict each other, such as being inferior in mechanical strength, and it is difficult to achieve both of them.

Examples of open-cell resin foams include urethane resins and melamine resins, which are mainly used as sponges that absorb fluids and cushioning materials that utilize flexibility and shock absorption. Because of their excellent sound absorption properties, they are widely used as sound absorbing materials that are lighter than inorganic materials. used as a constituent layer.

The main methods for producing foams include the bead foam molding method and the extrusion foam molding method. In the bead foam molding method, granular resin foam particles obtained by pre-expanding resin particles are formed into a desired shape. It is a method of molding by means of a mechanism that forms a molded product by thermal expansion and fusion of resin foam particles after being filled in a molding die. foam products can be manufactured with high productivity, there is no material loss that occurs in cutting, and molds for molding can be manufactured at low cost. This method is particularly preferable as a method for molding the material.
However, in the foam molding process of the bead foam molding method, the foam cells are closed cells separated by a resin film, and the mechanism of mutual fusion between the foam particles due to the expansion of the bubbles is used. Since the cell structure of is basically a closed cell structure, it is generally inferior in sound absorption performance.
On the other hand, a foam having a continuous pore structure, that is, a continuous pore structure provided in the foam by the bead foam molding method, and a method for producing the same have been proposed, and it is also known that the foam can be used as a sound absorbing foam material.

It is also known to improve sound absorption and sound insulation performance by laminating a resin foam with a single layer or a plurality of layers having different air permeability to form a laminate.

Patent Document 1 describes a sound-absorbing, sound-insulating, vibration-damping and heat-insulating cover, particularly for floor sound insulation, end wall sound insulation, door covers and roof inner covers, to provide noise reduction and heat insulation in vehicles. A multi-function kit for forming is described, the multi-function kit comprising at least one planar body part and a multi-layer noise reduction assembly package, the assembly package comprising at least one porous body part. a spring layer, in particular an open-pored foam layer, and a microporous hard layer, in particular an open-pored fiber layer or fiber/foam composite layer, said assembly package and said planar vehicle body part There is an air layer between them.

In Patent Document 2, a non-breathable layer is provided on one side of a porous base material layer containing a thermoplastic resin and reinforcing fibers, and the other side is provided with a layer higher than the thermoplastic resin, A breathable layer having a multi-layer structure including at least a heat-resistant thermoplastic resin layer and a skin bonding thermoplastic resin layer having a melting point lower than that of the non-breathable layer, and a skin layer are sequentially provided. A porous material is described in which a plurality of pores extending to the porous substrate layer are formed in the organic layer.

In Patent Document 3, at least one low-density elastic porous material layer having a density of 0.005 to 0.100 g/cm ³ and a low-permeability sheet having an air permeability of 10 cc/cm ² ·sec or less cover the periphery. describes a soundproof cover comprising a laminated material in which one or more high-density elastic porous layers having a density of 0.125 to 1.000 g/cm ³ are laminated.

Furthermore, in recent years, the current situation is that there is a demand for a thin structure with even better sound absorption and sound insulation performance in the low frequency range of around 1000 Hz, which is particularly required in the engine room of automobiles.

International Publication No. 98/18657 JP-A-2003-225959 JP 2017-167251 A

However, the sound absorbing materials described in Patent Documents 1 to 3 have room for improvement in terms of sound absorbing and insulating properties in the low frequency range. In addition, the sound absorbing material described in Patent Document 1 is not made of a hard material and does not stand on its own. In the sound absorbing material described in Patent Document 3, it is considered difficult to manufacture because it has a complicated structure in which a high-density porous body and a low-density porous body are combined. , each had problems.

Therefore, the problem to be solved by the present invention is to provide a multi-layered sound absorbing material that has high sound absorption and insulation performance even if it is thin in the low frequency range of 500 to 2000 Hz, especially in the low frequency range of around 1000 Hz, and is self-supporting. is.

As a result of intensive studies to solve the problem, the present inventors surprisingly found that a low-permeability resin layer having a specific thickness, a breathable resin foam layer having a specific porosity and thickness, and a specific thickness A multilayer sound absorbing material in which an air layer and a low-permeability resin layer having a specific air resistance are laminated in this order, or a layer of a specific thickness containing a fiber assembly having a specific air permeability is placed in the air layer. It was found that by forming a multi-layered sound absorbing material further provided in the above, it can be a suitable structural material that exhibits high sound absorbing and insulating performance in the low frequency range of 500 to 2000 Hz, especially around 1000 Hz, even if it is thin.
Furthermore, by selecting a thermoplastic resin having a specific range of surface tension or glass transition temperature as a raw material resin, mechanical strength, heat resistance, heat distortion resistance, flame retardancy, solvent resistance, and rigidity can be selected. The inventors have found that it can be a self-supporting sound absorbing structural material having a high level of sound absorbing and insulating performance, and completed the present invention.

That is, the present invention is as follows.
[1]
(A) a low-permeability resin layer with a thickness of 0.5 to 10 mm, (B) a breathable resin foam layer with a thickness (L) of 2 to 80 mm and a porosity of 15 to 97%, (B'') a thickness of 0 An air layer of 0.01 to 2.0 mm and (C) a low-permeability resin layer with a thickness (t) of 0.05 to 3.0 mm and a ventilation resistance of 20 kN s/m3 ^or more are laminated in this order. A multi-layered sound absorbing material characterized by comprising:
[2]
(A) Low air permeability resin layer with a thickness of 0.5 to 10 mm, (B) Air permeability resin foam layer with a thickness (L) of 2 to 80 mm and a porosity of 15 to 97%, (B''1) Thickness An air layer of 0.01 to 2.0 mm, (B') a layer having a thickness (t') of 0.1 to 4 mm containing a fiber aggregate having an air permeability of 2 to 70 cc/(cm ² ·sec), (B ''2) An air layer with a thickness of 0.01 to 2.0 mm, and (C) a low-permeability resin layer with a thickness (t) of 0.05 to 3.0 mm and a ventilation resistance of 20 kN s/m3 or ^more . , is laminated in this order.
[3]
(A) a low-permeability resin layer having a thickness of 0.5 to 10 mm; (B) a permeable resin foam layer having a porosity of 15 to 97%; has a plurality of concave holes on its surface, the thickness (L) of the part other than the part where the concave holes are provided is 2 to 80 mm, and the depth of the concave holes is 30 to 95 of the thickness (L) % and an open area ratio of 20 to 90%, (B''1) an air layer having a thickness of 0.01 to 2.0 mm, and (B') an air permeability of 2 to 70 cc/( cm ² sec) layer with a thickness (t′) of 0.1 to 4 mm containing a fiber aggregate, (B″2) an air layer with a thickness of 0.01 to 2.0 mm, and (C) airflow resistance A multilayer sound absorbing material characterized by laminating low-permeability resin layers having a thickness (t) of 0.05 to 3.0 mm and a thickness (t) of 20 kN·s/m ³ or more in this order.
[4]
The (B) air-permeable resin foam layer is a molded body in which resin foam particles having a recessed structure are fused to each other, and has continuous voids between the fused resin foam particles [1] The multilayer sound absorbing material according to any one of [3].
[5]
The fiber aggregate has a basis weight of 100 to 1000 g/m ² , an average apparent density of 0.10 to 1.0 g/cm ³ , and an average fiber diameter of 0.6 to 50 μm,
The multilayer sound absorbing material according to [2] or [3] , which has a thickness of 3 to 80 mm.
[6]
The (B) breathable resin foam layer contains a resin having a surface tension of 37 to 60 mN/m at 20°C, or a resin having a glass transition temperature of -10°C or higher and 280°C or lower, [1] to The multilayer sound absorbing material according to any one of [5].
[7]
The multilayer sound absorbing material according to any one of [1] to [6], which is a self-supporting sound absorbing body.

According to the present invention, it is possible to provide a self-supporting multi-layered sound absorbing material that has high sound absorption and insulation performance in the low frequency range of 500 to 2000 Hz, especially in the low frequency range of around 1000 Hz, even though it is thin.

FIG. 4 is a diagram showing an example of a cross-sectional view of resin foam particles that can be used for the multilayer sound absorbing material of the present embodiment. FIG. 3 is a perspective view of resin foam particles that can be used for the multilayer sound absorbing material of the present embodiment. It is a figure which shows sectional drawing (1st step) of the discharge port shape of the profile extrusion die used in the Example, and sectional drawing (2nd step) which shows the recessed structure part of the obtained resin foam bead. 1 is a schematic cross-sectional view of a multilayer sound absorbing material of this embodiment; FIG. (A) is an example of the multilayer sound absorbing material according to the first aspect of the present embodiment, (B) is an example of the multilayer sound absorbing material according to the second aspect of the present embodiment, and (C) is the present It is an example of a multilayer sound absorbing material according to the third aspect of the embodiment. FIG. 5 is a diagram showing the relationship between frequency and reverberant room sound absorption coefficient for examples and comparative examples of the multilayer sound absorbing material of the present embodiment. FIG. 4 is a diagram showing the relationship between frequency and sound transmission loss for examples and comparative examples of the multilayer sound absorbing material of the present embodiment.

[Multilayer sound absorbing material]
The first aspect of the multilayer sound absorbing material of the present embodiment includes (A) a low-permeability resin layer with a thickness of 0.5 to 10 mm, and (B) a thickness (L) of 2 to 80 mm with a porosity of 15 to 97%. (B'') an air layer having a thickness of 0.01 to ^2.0 mm; 0 mm low-permeability resin layers are laminated in this order.

The multi-layer sound absorbing material of the present embodiment includes (A) the low-permeability resin layer, (B) the air-permeable resin foam layer, (B'') the air layer, and (C) the low-permeability resin layer. , resin layer containing additives such as inorganic or organic particles, flame retardants, stabilizers, gas barrier layer, antistatic layer, hardened surface layer, electromagnetic shielding layer, lubricant layer, conductive layer, dielectric layer, electrical insulation layer , an anti-fogging layer, a magnetic layer, a printing layer, a decorative layer, and other layers. In addition, in order to impart design properties, a resin layer having a mirror surface or textured surface may be provided on the outermost surface.
Among them, the multilayer sound absorbing material of the present embodiment has (A) a low-permeability resin layer, (B) an air-permeable resin foam layer, (B'') an air layer, and (C) from the viewpoint of further excellent sound absorption performance. It is preferable to consist only of a low-permeability resin layer.
FIG. 4A is a schematic cross-sectional view of a first aspect of the multilayer sound absorbing material of this embodiment.

The thickness of the multilayer sound absorbing material of the present embodiment is preferably 3 to 80 mm, more preferably 5 to 50 mm, from the viewpoint of utilizing the rigidity for use as a self-supporting material and the lightness of the foam. It is preferably 3 to 30 mm, more preferably 3 to 30 mm.

((A) Low air permeability resin layer)
The (A) low-permeability resin layer having a thickness of 0.5 to 10 mm, which constitutes the multilayer sound absorbing material of the present embodiment, will be described below.
In the present specification, the term “low air permeability” of the (A) low air permeability resin layer means a state in which gas is blocked or almost impermeable, and the resin layer has an air resistance of 20 kN s/m ³ or more. and
The ventilation resistance can be measured by the method described in Examples below.

(A) Examples of the resin contained in the low-permeability resin layer include thermoplastic resins such as polystyrene, poly-α-methylstyrene, styrene maleic anhydride copolymer, blend or graft polymer of polyphenylene oxide and polystyrene, Styrenic polymers such as acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene terpolymer, styrene-butadiene copolymer, high impact polystyrene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, post-chlorinated polyvinyl chloride, ethylene or propylene and Vinyl chloride polymers such as vinyl chloride copolymers, polyvinylidene chloride copolymer resins, nylon-6, nylon-6,6, homo- and copolymer polyamide resins, polyethylene terephthalate, homo- and copolymer polyester resins, modified polyphenylene Ether resin (phenylene ether-polystyrene alloy resin), polycarbonate resin, methacrylimide resin, polyphenylene sulfide, polysulfone, polyethersulfone, polyester resin, phenol resin, urethane resin, polyolefin resin, and the like.
Examples of the polyolefin resin include polypropylene polymerized using a Ziegler catalyst or metallocene catalyst, ethylene-propylene random copolymer, propylene-butene random copolymer, ethylene-propylene block copolymer, ethylene-propylene-butene. Polypropylene resins such as terpolymers, low density polyethylene, medium density polyethylene, linear low density polyethylene, linear ultra-low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl Polyethylene-based resins such as methacrylate copolymers and ionomer resins may be used alone or in combination.
The above resins may be used singly or in combination of two or more.
Furthermore, for the purpose of controlling resin properties, etc., a resin in which inorganic or organic fillers such as glass fiber, glass particles, metal fibers, metal particles, carbon fibers, carbon particles, and cellulose fibers are appropriately dispersed and blended may be used. good.
Furthermore, within the range that does not impair the performance and characteristics of the multilayer sound absorbing material, (A) a single layer or multiple layers of an inorganic material such as glass, metal, metal oxide, etc., in the form of being laminated on a part of the low-permeability resin layer It is also possible to use a thin layer of

(A) The thickness of the low-permeability resin layer is 0.5 to 10 mm, preferably 0.6 to 8 mm, and more preferably 0.8 to 6 mm, from the viewpoint of achieving both sound insulation and lightness. is more preferable.

((B) Breathable resin foam layer)
The (B) air-permeable resin foam layer having a porosity of 15 to 97% and a thickness (L) of 2 to 80 mm, which constitutes the multilayer sound absorbing material of the present embodiment, will be described below.

(B) The breathable resin foam layer is preferably a molded body in which resin foam particles having concave structures are fused to each other, and may have continuous voids between the fused resin foam particles. preferable. That is, the (B) breathable resin foam layer of the present embodiment is preferably a molded body having at least a portion in which at least two or more resin foam particles are fused together. There are fused parts and voids between the fused resin foam particles.
Moreover, the molded article is preferably a molded article obtained by fusion molding resin foam particles.

(B) The thickness (L) of the breathable resin foam layer is 2 to 80 mm, preferably 3 to 50 mm, more preferably 5 to 20 mm, from the viewpoint of achieving both sound absorption and thickness reduction. more preferred.

(B) The air-permeable resin foam layer has continuous voids between the fused resin foam particles as described above, and the porosity is 15 to 97% from the viewpoint of sound insulation and rigidity of the multilayer sound absorbing material. , preferably 20 to 95%, more preferably 30 to 90%.
(B) A method for controlling the porosity of the breathable resin foam layer includes, for example, adjusting the shape of the recessed structure of the resin foam beads. The porosity tends to increase as the depth is increased, and the porosity tends to decrease as the depth of the concave structure portion of the foamed resin bead is decreased. It is also possible to control the expansion rate of particles during molding within a range that does not reduce the mutual fusion of particles during molding.
The porosity can be measured by the method described in Examples below.

The (B) air-permeable resin foam layer of the present embodiment is a molded body obtained by fusion bonding aggregates of resin foam particles to each other, and preferably has continuous voids between the resin foam particles. .
As used herein, the term “continuous void” refers to the formation of mutually continuous voids between the fused resin foam particles. It means that a continuous void is generated in the , and the fluid is in a state where it can flow. The molded article of the present embodiment preferably has voids that are continuous in at least one direction, and preferably has voids that are continuous in the thickness direction.
In the present embodiment, as the continuous void, a sample of the (B) breathable resin foam layer with a thickness of 10 mm is used, and the unit measured in the thickness direction is measured by the AC method specified in the international standard ISO 9053. Length flow resistance is preferably 1,000,000 N·s/m ⁴ or less, more preferably 500,000 N·s/m ⁴ or less, and still more preferably 200,000 N·s/m ⁴ or less .

(B) The fusion bonding strength of the air-permeable resin foam layer is evaluated by measuring the tensile strength based on JIS K6767A and (B) breaking elongation (%) of the air-permeable resin foam layer. The breaking elongation is preferably 1% or more, more preferably 2% or more. If the elongation at break is less than 1%, the air-permeable resin foam layer (B) may be damaged by vibrations during running or vibrations of the power system when installed in an engine room.

(B) The air-permeable resin foam layer is produced by filling the resin foam particles into a closed mold and foaming them. may be adopted. A general-purpose in-mold foaming automatic molding machine can be used depending on the type of resin and molding conditions.

-Resin foamed particles-
(B) The resin foam particles constituting the air-permeable resin foam layer are not particularly limited as long as they are capable of forming the above-described voids. It may be a resin foamed particle having a concave portion in the external shape viewed from the outside, or a particle having a general shape as a resin foamed particle such as an elliptical sphere, a columnar shape, or a polygonal columnar shape. Resin foamed particles having
In the present embodiment, resin foamed particles having a recessed structure and resin foamed particles having a general shape such as an elliptical sphere, a cylinder, or a polygonal prism without a recessed structure are mixed and used at an arbitrary ratio. By manufacturing the molded article by using the above method, it is possible to adjust the desired balance between sound absorption performance and mechanical strength.
In this specification, having a concave structure means that there is a direction in which an orthogonal projection image of the foamed resin bead becomes a concave figure. In this specification, a concave figure means that at least a part (preferably, the whole line segment) of a line segment connecting two points on the outer surface of the orthogonal projection image figure to be a concave figure is an external region of the resin foam beads. It means that it is possible to choose two points that will be a line segment that passes through. An example of a concave figure is shown in FIG.
Further, the recessed structure portion has a structure different from that of foamed cells formed during foaming.

There may be one or a plurality of concave structures.
The recessed structure portion may be one or more through-holes connecting the surfaces of the foamed resin particles, one or more recesses that do not penetrate the particles, or one or more through-holes and one or more recesses may be mixed. Here, the through-hole may be a cavity connecting two holes formed on the outer surface of the resin foamed bead. The structure may be such that a projection image (an orthographic projection image in which the cavity forms an isolated cavity within the foamed resin particles) can be obtained.

In the expanded resin bead, the concave portion is defined by a straight line that circumscribes the area occupied by the expanded resin bead in an orthographic projection image in which the concave portion can be confirmed, and the outer surface of the expanded resin bead. The ratio of the region A (region A/region occupied by the expanded resin particles) is preferably 10% or more, more preferably 30% or more. Above all, it is preferable that the orthogonal projection image including the deepest part of the concave portion satisfies the above range. Here, the deepest part of the recess may be the part where the distance to the intersection of the straight line perpendicular to the recess at least at two points or more and the outer surface of the recess is the longest.

When the recessed structure portion is a through-hole, the area of the through-hole should be 10% or more of the total area of the orthographic projection image of the expanded resin bead, in which the through-hole can be confirmed in the expanded resin bead. is preferred, and more preferably 30% or more. Above all, it is preferable that the above range is satisfied in an orthographic image in which the area of the through-holes of the expanded resin beads is the largest. In addition, in the cross section where the hollow shape passing through the through hole can be confirmed, the area of the hollow shape is preferably 10% or more, more preferably 30%, with respect to the total area of the expanded resin beads on the cross section. % or more. The through-hole preferably has at least one cross-section in which the area of the hollow shape satisfies the above, and more preferably the entire cross-section satisfies the above range.

By selecting the shape of the foamed resin particles such that the recessed structure satisfies the conditions for the recesses and/or the conditions for the through holes, the continuous voids (continuous voids, Communicating voids) can be formed satisfactorily.

Although the recessed structure portion of the resin foamed bead may or may not be a through hole, it is particularly preferable that the resin foamed bead has a shape having a recessed portion. By adopting a shape with recesses, there is a filling state that conventional foamed resin particles did not have, and the structure of the communicating voids of the molded product obtained after molding achieves a particularly excellent balance of both sound absorption performance and mechanical strength. can do.

A particularly excellent shape as the shape having the recesses is a structure in which groove-shaped recesses are provided in the foamed resin particles. When the particles are joined in a filled state in which the particles are engaged, a molded body having a large joining area between the resin foam particles and a high strength is formed. A void extending between the resin foam particles, that is, a communicating void is formed.
As the groove-shaped concave portion, for example, a shape (FIGS. 2A and 2B) obtained by overlapping cross sections (FIG. 1) of a shape (C shape, U shape, etc.) obtained by cutting a part of a hollow substantially circle (FIGS. 2A and 2B), a hollow and a shape in which cross sections (FIG. 1) obtained by partially cutting out approximately polygons (triangles, quadrilaterals, etc.) of are overlapped. Here, the hollow in the hollow substantially circle and the hollow substantially polygon may be substantially circular or substantially polygonal, but preferably has the same shape as the shape surrounding the hollow. . Moreover, it is preferable that the center of the hollow shape and the center of the shape surrounding the hollow overlap (for example, a concentric circle).

Examples of the recess include, for example, a saddle-shaped shape formed by bending a disk shape having a certain thickness, a shape formed by bending or bending a disk in the out-of-plane direction, and a single or multiple recesses on the outer surface of a cylindrical shape. structure provided with a concave portion. Among the particle shapes, an example of a particle shape that is particularly preferable in terms of ease of production, excellent productivity, and easy control of the shape is a cylindrical shape having a common axis with an outer diameter smaller than the outer diameter. Examples include a shape (FIG. 2) obtained by cutting out and cutting out a portion within a certain angle when viewed from the axial direction of a cylinder obtained by cutting a column of height. Hereinafter, this shape is referred to as a C-shaped cross-sectional partial cylindrical shape, and even if it is substantially the same shape that is slightly deformed based on this shape, it is possible to form an equivalent gap in the molded body, If the above conditions are satisfied, it can be used within the scope of the present invention. FIG. 2 shows a preferred example of a C-shaped cross-section partial cylinder having different sizes of portions to be cut and cut.

It is preferable that the concave portions have the same shape when the cross section is continuously formed in one specific direction of the foamed resin beads. For example, as shown in FIG. 2, the shape of the concave portion in a cross section in one direction (vertical direction in FIG. 2, extrusion direction) of the foamed resin particle is the same as the shape of the concave portion in a different cross section formed by being shifted in the one direction. Preferably.

It can be confirmed by observing and judging transmission images of the expanded resin beads with an optical microscope while changing the observation direction of the particles that the expanded resin beads have concave structures.

In the expanded resin beads, the ratio ρ ₀ /ρ ₁ between the density ρ ₀ of the resin contained in the expanded resin beads and the true density ρ ₁ of the expanded resin beads is preferably 2.0 to 20, more preferably 2. .2 to 18, more preferably 2.5 to 15. When ρ ₀ /ρ ₁ is less than 2.0, the sound absorbing performance is not sufficiently developed, and when it exceeds 20, the mechanical strength is lowered, which is not preferable.

In the expanded resin beads, the ratio ρ ₁ /ρ ₂ between the true density ρ ₁ of the expanded resin beads and the bulk density ρ ₂ of the expanded resin beads is preferably 1.5 to 4.0, more preferably 1. 8 to 3.5, more preferably 2.0 to 3.0. If ρ ₁ /ρ ₂ is less than 1.5, the sound absorbing performance is not sufficient, and if it exceeds 4.0, the mechanical strength is lowered, which is not preferable.

In this specification, the bulk density ρ ₂ is a value M/V ₂ obtained by dividing a predetermined weight M of the expanded resin beads by the bulk volume V ₂ of the expanded resin beads at that weight M, and the true density ρ ₁ is the predetermined weight. It is a value M/ _V1 obtained by dividing M resin expanded beads by the true volume _V1 of the resin expanded beads at the weight M. The bulk volume _V2 refers to the value obtained by filling a graduated cylinder with the foamed resin particles of the predetermined weight M, vibrating the graduated cylinder, and reading the scale when the volume reaches a constant weight. Further, the true volume _V1 means the volume of the portion increased by the liquid when the foamed resin beads of the predetermined weight M are submerged in a graduated cylinder containing a liquid that does not dissolve the foamed resin beads.
The density ρ ₀ of the resin is the density of the raw material resin before foaming, and is the density measured by the submersion method using a weighing scale.
In this specification, ρ ₀ , ρ ₁ , and ρ ₂ all mean values obtained by measurement under an environment of 20° C. and 0.10 MPa.

The average particle size of the resin foamed beads can be measured by classifying 100 g of resin foamed beads using a standard sieve defined by JIS Z8801. The average particle diameter of the expanded resin particles is preferably 0.5 to 6.0 mm, more preferably 0.7 to 5.0 mm. If the average particle size is less than 0.5 mm, it is difficult to handle in the manufacturing process, and if it exceeds 6.0 mm, the surface accuracy of complicated molded articles tends to decrease, which is undesirable.
The shape of the foamed resin particles of the present embodiment is not particularly limited, and may be various shapes.

As a method for producing the resin foamed particles, a method utilizing the thermoplasticity of thermoplastic resin, a method by post-processing such as cutting of particles in a solid state, and the like are possible, and any method that can impart a desired shape to the particles can be used. applicable if Among them, a profile extrusion method using a die having a discharge cross section of a special shape can be suitably used as a method capable of producing particles having a stable shape with excellent productivity. Thermoplastic resin is melt-extruded by an extruder having a die with a specially shaped discharge cross section, and pelletized by a method commonly used industrially such as strand cutting or underwater cutting. A method of obtaining particles, a method of injecting a foaming agent into an extruder from the middle of a barrel, foaming at the same time as discharge, cooling, and then underwater cutting or strand cutting to obtain resin foamed particles directly, melting in an extruder to obtain a desired cross-sectional shape and then cut to a predetermined length with a pelletizer after cooling to produce resin pellets. The resin pellets are impregnated with a foaming agent and heated to foam at a predetermined expansion ratio. It can be manufactured by applying any known method.

The foamed resin particles contain a resin. Examples of the resin include thermoplastic resins.
Examples of the thermoplastic resin include polystyrene, polyα-methylstyrene, styrene maleic anhydride copolymer, blend or graft polymer of polyphenylene oxide and polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene terpolymer, styrene-butadiene. Copolymers, styrenic polymers such as high impact polystyrene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, post-chlorinated polyvinyl chloride, vinyl chloride polymers such as copolymers of ethylene or propylene and vinyl chloride, polyvinylidene chloride Copolymer resins, nylon-6, nylon-6,6, homo- and copolymer polyamide resins, polyethylene terephthalate, homo- and copolymer polyester resins, modified polyphenylene ether resins (phenylene ether-polystyrene alloy resins), polycarbonate resins, methacrylimide Resins, polyphenylene sulfides, polysulfones, polyethersulfones, polyester resins, phenol resins, urethane resins, polyolefin resins, and the like can be used.

Examples of the polyolefin resin include polypropylene polymerized using a Ziegler catalyst or metallocene catalyst, ethylene-propylene random copolymer, propylene-butene random copolymer, ethylene-propylene block copolymer, ethylene-propylene-butene. Polypropylene resins such as terpolymers, low density polyethylene, medium density polyethylene, linear low density polyethylene, linear ultra-low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl Polyethylene-based resins such as methacrylate copolymers and ionomer resins may be used alone or in combination.

The resin preferably has a surface tension of 37 to 60 mN/m at 20° C., more preferably 38 to 58 mN/m, still more preferably 39 to 55 mN/m. If the surface tension is within the above range, a sound-absorbing molded article with high mechanical strength can be obtained, which is particularly preferable.
As the surface tension of the resin, the value measured by the method described in JIS K6768 "Plastics--Film and sheet--Wet tension test method" but changing the temperature to 20.degree.

Particularly preferred thermoplastic resins include polyamide resins, polyester resins, polyether resins, methacrylic resins, modified polyether resins (phenylene ether-polystyrene alloy resins), etc., and thermoplastic resins having a surface tension within the above range. Among them, polyamide resin has excellent heat resistance, chemical resistance, and solvent resistance, and is suitable for use as a highly heat-resistant foam structure material. Modified polyether resin (phenylene ether-polystyrene alloy resin).

By setting the surface tension of the resin within the above range, especially when the foamed resin is thermally expanded and fused with superheated steam, the affinity between the water vapor and the surface increases, resulting in a uniform foamed molded product with high fusion strength. be done. The surface tension of the resin may be the surface tension of the mixed resin of all the resins constituting the resin foamed beads, and the surface tension of at least one resin among all the resins constituting the resin foamed beads satisfies the above range. More preferably, the surface tension of all the resins satisfies the above range.

The resin preferably has a glass transition temperature of −10° C. or higher and 280° C. or lower.
As the glass transition temperature of the resin, a value measured by the DSC method in accordance with JIS K7121:1987 "Method for measuring transition temperature of plastics" is used. That is, after conditioning for at least 24 hours at 23±2° C. and 50±5% relative humidity, the specimen was placed in the container of the DSC instrument and, if amorphous, was treated at a temperature at least about 30° C. above the end of the glass transition. to at least about 30° C. above the end of the melting peak, if crystalline, and held at each temperature for 10 minutes, followed by quenching to about 50° C. below the glass transition temperature. The heating rate is maintained at a temperature about 50° C. lower than the transition temperature until the device stabilizes, and then heated at a heating rate of 20° C. per minute to a temperature about 30° C. higher than the end of the transition, and a DSC curve is drawn.

The lower limit of the glass transition temperature of the resin raw material is more preferably 0°C, still more preferably 10°C. By making the glass transition temperature equal to or higher than the above lower limit, it is possible to suppress deterioration of the sound absorbing performance due to long-term compressive force applied to the molded product, and it is preferable in that it can be used for sound absorbing members to which stress is applied.

The upper limit of the glass transition temperature is more preferably 260°C, still more preferably 240°C. When the glass transition temperature is not higher than the above upper limit, the temperature for foam molding can be set low, and the foam can be manufactured with high productivity, which is particularly preferable.

Examples of thermoplastic resins included in the preferred glass transition temperature range include polyamide resins, polyester resins, polyether resins, methacrylic resins, modified polyether resins (phenylene ether-polystyrene alloy resins), etc., and the glass transition temperature is Thermoplastic resins within the above range can be mentioned.
Among them, polyamide resin has excellent heat resistance, chemical resistance, and solvent resistance, and is suitable for use as a highly heat-resistant foam structure material. Modified polyether resin (phenylene ether-polystyrene alloy resin).
The glass transition temperature of the resin may be the glass transition temperature of the mixed resin of all the resins constituting the resin foamed beads, and at least one resin among all the resins constituting the resin foamed beads has the above glass transition temperature. It is preferable that the range is satisfied, and it is more preferable that the glass transition temperatures of all the resins satisfy the above range.

The above thermoplastic resin may be used in an uncrosslinked state. It may be crosslinked by peroxide, radiation, or the like.

The foamed resin particles may optionally contain conventional compounding agents such as antioxidants, light stabilizers, ultraviolet absorbers, flame retardants, coloring agents such as dyes and pigments, plasticizers, lubricants, crystallization nucleating agents, Inorganic fillers such as talc and calcium carbonate may be included depending on the purpose.

As the flame retardant, a bromine-based, phosphorus-based, etc. flame retardant can be used, and as the antioxidant, a phenol-based, phosphorus-based, sulfur-based, etc. antioxidant can be used. Hindered amine-based, benzophenone-based light stabilizers and the like can be used as the agent.

If it is necessary to adjust the average cell diameter of the expanded resin beads, a cell control agent may be added. Inorganic nucleating agents include talc, silica, calcium silicate, calcium carbonate, aluminum oxide, titanium oxide, diatomaceous earth, clay, sodium bicarbonate, alumina, barium sulfate, aluminum oxide, bentonite, and the like. The amount to be used is usually 0.005 to 2 parts by mass based on the total amount of raw materials for the expanded resin particles.

A volatile foaming agent etc. are mentioned as a foaming agent used at the time of manufacture of the said expanded resin bead. Examples of the volatile foaming agent include chain or cyclic lower aliphatic hydrocarbons such as methane, ethane, propane, butane, isobutane, pentane, isopentane, neopentane, hexane, heptane, cyclopentane, cyclohexane, and methylcyclopentane; Halogenated hydrocarbons such as dicyclodifluoromethane, trichloromonofluoromethane, 1-chloro-1,1-difluoroethane, 1-chloro-2,2,2-trifluoroethane; inorganics such as nitrogen, air, and carbon dioxide; A gas-based foaming agent and the like are included.

((B'') air layer)
The (B'') air layer having a thickness of 0.01 to 2.0 mm, which constitutes the multilayer sound absorbing material of this embodiment, will be described below.
The (B'') air layer is a gap layer formed between the (B) air-permeable resin foam layer and the (C) low-air-permeability resin layer.
(B'') The air layer can be formed, for example, by partially adhering (B) the air-permeable resin foam layer and (C) the low air-permeability resin layer. The state in which both layers are partially adhered is not particularly limited, and examples include a state in which both layers are adhered at a plurality of points, a state in which only edges of both layers are adhered, and the like.
Also, (B'') the air layer may be formed by simply stacking (B) the air-permeable resin foam layer and (C) the low air-permeability resin layer. In this case, there is a method of fitting both layers into a predetermined frame and fixing at least the ends so that an air layer (B'') is formed between both layers.

(B'') The thickness of the air layer is the thickness of the interstitial layer of air contained in the layer. After that, it is measured by a method of measuring a cut surface or the like, and evaluated as an average value in the plane direction. In the case of a multilayer sound absorbing material with a surface area of S mm ² , the average value in the plane direction is the area T mm ² where (B) the air-permeable resin foam layer and (C) the low air-permeability resin layer are bonded. Area excluding the part (ST) mm ² Defined as the average value for the part, the cross-sectional area of the air layer in the cut plane perpendicular to the surface of the multilayer sound absorbing material When the total volume of the air layer obtained by integrating over the above area (ST) mm ² is V mm ³ , it is obtained as V/(ST) mm. An average value calculated from a representative value of a portion sampled in the plane may be used as long as the method can appropriately evaluate the average value in the plane direction.
The thickness of the (B'') air layer defined as above is 0.01 to 2.0 mm and 0.03 to 0.8 mm from the viewpoint of achieving both sound absorption and shape stability. is preferred, and 0.05 to 0.5 mm is more preferred.

((C) Low air permeability resin layer)
The (C) low-permeability resin layer having a thickness (t) of 0.05 to 3.0 mm and having a ventilation resistance of 20 kN·s/m ³ or more, which constitutes the multilayer sound absorbing material of the present embodiment, will be described below.
In this specification, the “low air permeability” of the (C) low air permeability resin layer means a state in which gas is blocked or almost impermeable.

(C) The ventilation resistance of the low-permeability resin layer is 20 kN s/m ³ or more, preferably 30 kN s/m ³ or more, and 40 kN s/m from the viewpoint of the frequency characteristics of sound absorption performance. ³ or more is more preferable.
(C) As a method of controlling the ventilation resistance of the low-permeability resin layer, for example, (C) providing a through-hole in the low-permeability resin layer can be mentioned. The airflow resistance can be reduced as the number of is increased. Methods for increasing airflow resistance include reducing the number of defects in the resin layer or intentionally provided through holes and/or reducing their size (diameter).
The ventilation resistance can be measured by the method described in Examples below.

(C) The thickness (t) of the low-permeability resin layer is 0.05 to 3.0 mm, and 0.07 to 2, from the viewpoint of achieving both the frequency dependence of the sound absorption coefficient and the durability of the multilayer sound absorbing material. 0.5 mm, more preferably 0.09 to 2.0 mm.

(C) Examples of the resin contained in the low-permeability resin layer include thermoplastic resins such as polystyrene, poly-α-methylstyrene, styrene maleic anhydride copolymer, blend or graft polymer of polyphenylene oxide and polystyrene, Styrenic polymers such as acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene terpolymer, styrene-butadiene copolymer, high impact polystyrene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, post-chlorinated polyvinyl chloride, ethylene or propylene and Vinyl chloride polymers such as vinyl chloride copolymers, polyvinylidene chloride copolymer resins, nylon-6, nylon-6,6, homo- and copolymer polyamide resins, polyethylene terephthalate, homo- and copolymer polyester resins, modified polyphenylene Ether resin (phenylene ether-polystyrene alloy resin), polycarbonate resin, methacrylimide resin, polyphenylene sulfide, polysulfone, polyethersulfone, polyester resin, phenol resin, urethane resin, polyolefin resin, and the like.
Examples of the polyolefin resin include polypropylene polymerized using a Ziegler catalyst or metallocene catalyst, ethylene-propylene random copolymer, propylene-butene random copolymer, ethylene-propylene block copolymer, ethylene-propylene-butene. Polypropylene resins such as terpolymers, low density polyethylene, medium density polyethylene, linear low density polyethylene, linear ultra-low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl Polyethylene-based resins such as methacrylate copolymers and ionomer resins may be used alone or in combination.
The above resins may be used singly or in combination of two or more.

A lamination method of (A) a low-permeability resin layer, (B) a permeable resin foam layer, (B'') an air layer, and (C) a low-permeability resin layer in the multilayer sound absorbing material of the present embodiment will be explained. do.

Examples of means for laminating the (B) breathable resin foam layer on one side of the (A) low-air-permeable resin layer include a method of thermal bonding and a method of lamination and integration via an adhesive. The (A) low-air-permeability resin layer and (B) the air-permeability resin foam layer may be simply overlapped and laminated without using an adhesive. By not using an adhesive or the like, air permeability can be reliably secured between the (A) low-air-permeable resin layer and (B) the air-permeable resin foam layer, and stable sound absorption performance can be maintained. . In this way, in the case of simply overlapping and stacking, it is preferable to integrate them by fitting them into a predetermined frame and fixing at least the ends.

When (A) the low-air-permeability resin layer and (B) the air-permeable resin foam layer are laminated and integrated via an adhesive, it is preferable to secure air permeability by partially arranging the adhesive. When the adhesive forms a film and becomes an adhesive layer, and air permeability is impaired, the penetration of sound from the (B) air-permeable resin foam layer to the (A) low-air-permeability resin layer is hindered, and the sound absorption performance is reduced. It is likely to decline. As a method for making the adhesive exist partially in this way, it is preferable to use a powdery or fibrous thermal adhesive.

As a specific example of the method of laminating (A) the low-permeability resin layer and (B) the air-permeable resin foam layer by thermal bonding, (A) the resin contained in the low-permeability resin layer and (B) the air-permeability A thermal bonding method in which the resin contained in the resin foam layer is heated and pressed with a net, rolls, etc. under a heated atmosphere in which the resin softens or melts; Adhesion method in which hot-melt powder, adhesive, etc. is applied to the resin foam layer by spraying, rolling, etc., and is joined by heat treatment, etc.; , an adhesive sheet method in which a sheet-like material such as a tape yarn cloth, a photomelt film, or a mesh is interposed for bonding, and a method in which a tucker or a nail is driven in to fix the adhesive sheet. The bond may be adhered at multiple points.

Next, (B'') an air layer is formed between (B'') air layers (C ) laminating a low-permeability resin layer.
As means for laminating (A) a low-permeability resin layer and (C) a low-permeability resin layer so that (B'') an air layer is formed between them, there is a method other than partial heat bonding. , a method of partially laminating and integrating via an adhesive, etc., but without using an adhesive, (A) the low-permeability resin layer and (C) the low-permeability resin layer are simply superimposed. May be laminated. Each lamination method can be carried out in the same manner as the method for laminating (A) the low-air-permeability resin layer and (B) the air-permeability resin foam layer described above.

The multilayer sound absorbing material of this embodiment is used with the (C) low-permeability resin layer side positioned on the sound incident side. (C) By locating the low-permeability resin layer side on the sound incident side, the sound absorption performance can be effectively improved.

In the multilayer sound absorbing material of the present embodiment, (B) the air-permeable resin foam layer alone has low sound absorption performance in the entire frequency range, and the higher the frequency, the higher the sound absorption coefficient tends to be, but (A) low air permeability A resin layer, (B) an air-permeable resin foam layer, (B'') an air layer, and (C) a low air-permeability resin layer are laminated in this order to achieve a sound absorption coefficient in the low frequency range of 500 to 2000 Hz. increases, it is possible to exhibit high sound absorption especially around 1000 Hz, and it is possible to suppress low-frequency noise around 1000 Hz generated in the engine room of an automobile.
FIG. 5 shows the relationship between the frequency and the reverberant room sound absorption coefficient in the example described later.

The sound absorption coefficient at 1000 Hz of the multilayer sound absorbing material of this embodiment is preferably 0.25 or more, more preferably 0.30 or more.
The sound absorption coefficient can be measured by the method described in Examples below.

In addition, the multilayer sound absorbing material of the present embodiment has (C) a low-permeability resin layer on the outermost surface on the sound source side, (A) a low-permeability resin layer on the outermost surface on the side opposite to the sound source, and further (B ) By providing an air layer (B'') on the sound source side of the air-permeable resin foam layer, it is possible to exhibit sound insulation performance that surpasses existing sound absorbing materials in the entire frequency range.
FIG. 6 shows the relationship between frequency and sound transmission loss in the example described later.

The transmission loss at 1000 Hz of the multilayer sound absorbing material of this embodiment is preferably 10 dB or more, more preferably 12 dB or more.
The transmission loss can be measured by the method described in Examples below.

The multi-layered sound absorbing material of this embodiment can be used as a member for shielding various noises, for example, as a sound insulating member in an engine room of a vehicle such as an automobile. In particular, by selecting a hard thermoplastic resin for the (B) air-permeable resin foam layer, a self-supporting sound absorbing body that can stand on its own with only the multilayer sound absorbing material of this embodiment without further laminating other members. can be used.

The second aspect of the multilayer sound absorbing material of the present embodiment includes (A) a low-permeability resin layer with a thickness of 0.5 to 10 mm, (B) a thickness (L) with a porosity of 15 to 97% and a thickness (L) of 2 to 80 mm. Breathable resin foam layer, (B''1) an air layer with a thickness of 0.01 to 2.0 mm, and (B') a thickness including a fiber assembly with an air permeability of 2 to 70 cc/(cm ² ·sec) (t′) a layer of 0.1 to 4 mm, (B″2) an air layer of 0.01 to 2.0 mm in thickness, and (C) a thickness (t) with a ventilation resistance of 20 kN s/m ³ or more Low air permeability resin layers of 0.05 to 3.0 mm are laminated in this order.

The multilayer sound absorbing material of the present embodiment includes the above (A) low-permeability resin layer, (B) air-permeable resin foam layer, (B''1) air layer, (B') layer, (B''2) ) air layer and (C) low-permeability resin layer, other layers described above may be included. In addition, in order to impart design properties, a resin layer having a mirror surface or textured surface may be provided on the outermost surface.
Among them, the multilayer sound absorbing material is composed of (A) a low-permeability resin layer, (B) a permeable resin foam layer, (B''1) an air layer, (B') a layer, ( It is preferable to consist only of B''2) an air layer and (C) a low-permeability resin layer.
FIG. 4B is a schematic cross-sectional view of a second aspect of the multilayer sound absorbing material of this embodiment.

In the second aspect of the multilayer sound absorbing material of the present embodiment, the thickness of the multilayer sound absorbing material is preferably within the range described above.

((A) Low air permeability resin layer)
In the second aspect of the multilayer sound absorbing material of the present embodiment, the (A) low-permeability resin layer described above can be used as the (A) low-permeability resin layer.

((B) Breathable resin foam layer)
In the second aspect of the multilayer sound absorbing material of the present embodiment, the (B) air-permeable resin foam layer described above can be used as the (B) air-permeable resin foam layer.

((B''1) air layer and (B''2) air layer)
In the second aspect of the multilayer sound absorbing material of the present embodiment, (B''1) air layer and (B''2) air layer can be formed in the same manner as (B'') air layer described above. can. The preferable range of thickness is also the range described above.

((C) Low air permeability resin layer)
In the second aspect of the multilayer sound absorbing material of the present embodiment, the (C) low-permeability resin layer described above can be used as the (C) low-permeability resin layer.

((B') layer)
(B') Thickness (t') of 0.1 to 4 mm including a fiber aggregate having an air permeability of 2 to 70 cc/(cm ² ·sec), which constitutes the second aspect of the multilayer sound absorbing material of the present embodiment. layers are described below.

The (B') layer contains a fiber aggregate having an air permeability of 2 to 70 cc/(cm ² ·sec).
In addition to the fiber assembly, the layer (B') contains antioxidants, light stabilizers, ultraviolet absorbers, flame retardants, coloring agents such as dyes and pigments, plasticizers, lubricants, crystallization nucleating agents, and talc. , a resin phase containing an inorganic filler such as calcium carbonate. In addition, for the purpose of imparting coloration, water repellency, flame retardancy, etc., to the layer (B'), functions such as coloring processing such as dyeing, water repellent processing such as fluorine resin, and flame retardant processing such as phosphorus are added. It can be processed.

(B') The thickness (t') of the layer is 0.1 to 4 mm, preferably 0.3 to 3 mm, from the viewpoint of compatibility between the frequency range of the sound absorbing performance and the shape maintenance and durability of the multilayer sound absorbing material. , more preferably 0.5 to 2 mm.

The air permeability of the layer (B') is preferably 2 to 70 cc/(cm ² ·sec), more preferably 3 to 60 cc/(cm ² ·sec), still more preferably 4 to 40 cc/(cm ^{2 )} . · sec). When the air permeability is within the above range, the frequency characteristics of the sound absorbing performance can be well controlled.
The air permeability of the layer (B') can be measured by the same method as the method for measuring the air permeability of the fiber assembly, which will be described later.

-Fiber assembly-
The fiber aggregate contained in the layer (B') may be an aggregate of one type of fiber, or may be an aggregate of multiple types of fibers. Further, the fiber assembly may be a single layer body composed of one fiber layer, or may be a laminate body composed of a plurality of fiber layers. The form of the fiber assembly is not particularly limited, and may be, for example, any form such as woven fabric, non-woven fabric, or felt.

Specific examples of the resin constituting the fiber assembly include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene 1,4-cyclohexanedimethanol (PCT), polylactic acid (PLA) and/or Alternatively, thermoplastic polymers such as polypropylene (PP), polyacrylonitrile, polyacetate, and polyamide resins may be used. Of these, PET, PP, and polyamide can be used in terms of cost and ease of processing. Furthermore, from the viewpoint of weight reduction, PP with a lighter specific gravity can be used.

The fiber assembly has an air permeability of 2 to 70 cc/(cm ² ·sec), preferably 3 to 60 cc/(cm ² ·sec), more preferably 4 to 50 cc/(cm ² ·sec). If ^{the air permeability is less than 2 cc/(cm 2 ·} sec), the sound absorption performance will decrease on average. This is not preferable because it narrows the indicated frequency range.
The air permeability of the fiber assembly can be measured by the method described in Examples below.

The weight per unit area (basis weight) of the fiber assembly is preferably 100 to 1000 g/m ² , more preferably 200 to 900 g/m ² , still more preferably 300 to 800 g/m ² . If the basis weight is less than 100 g/m ² , the sound absorption performance of the multi-layered sound absorbing material is lowered, and if the basis weight of the fiber assembly exceeds 1000 g/m ² , the durability tends to be lowered, which is undesirable.
The fabric weight of the fiber assembly can be measured by the method described in Examples below.

The average apparent density of the fiber assembly is preferably 0.10 to 1.0 g/cm ³ , more preferably 0.15 to 0.9 g/m ³ , still more preferably 0.20 to 0.8 g. / ^m3 . If the average apparent density is less than 0.10 g/cm ³ , the sound absorbing performance of the multilayer sound absorbing material is reduced, and if the average apparent density of the fiber assembly exceeds 1.0 g/cm ³ , the denseness increases, ( B) The adhesion stability with the air-permeable resin foam layer is lowered.
The average apparent density of the fiber assembly can be measured by the method described in Examples below.

The fiber assembly preferably has an average fiber diameter of 0.6 to 50 μm, more preferably 0.8 to 40 μm, still more preferably 1.0 to 30 μm. When the average fiber diameter is less than 0.6 μm, the durability of the layer (B′) tends to decrease, and when the average fiber diameter exceeds 50 μm, the sound absorption coefficient tends to decrease, which is not preferable.
The average fiber diameter of the fiber assembly can be measured by the method described in Examples below.

The thickness of the fiber assembly is preferably 0.1 to 4 mm, more preferably 0.15 to 3 mm, and even more preferably 0.2 to 0.2 mm, from the viewpoint of achieving both the frequency characteristics of sound absorption performance and shape stability. 2 mm.

(A) low-permeability resin layer, (B) air-permeable resin foam layer, (B''1) air layer, (B') layer, (B''2) air in the multilayer sound absorbing material of the present embodiment A method of laminating the layer and (C) the low-permeability resin layer will be described.

The means for laminating (B) the air-permeable resin foam layer on one side of the (A) low-air-permeability resin layer can use the above-described lamination means.

On the surface of the (B) air-permeable resin foam layer to which the (A) low-permeability resin layer is not adhered, (B''1) an air layer is formed (B'). Examples of means for laminating layers include a method of partially heat-bonding, a method of partially laminating and integrating via an adhesive, and the like. The foam layer and the (B') layer may be laminated by simply overlapping each other. In this way, in the case of simply overlapping and stacking, it is preferable to integrate them by fitting them into a predetermined frame and fixing at least the ends.
When the (B) air-permeable resin foam layer and the (B') layer are partially laminated and integrated via an adhesive, a powdery or fibrous thermal adhesive may be used.
As a specific example of the lamination method by partially heat-bonding the (B) air-permeable resin foam layer and the (B') layer, (B) the resin contained in the air-permeable resin foam layer, and (B) ') A thermal bonding method in which the fibers contained in the layer are heated and pressed with a net, roll, etc. under a heated atmosphere that softens or melts; (B) Breathable resin foam layer and / or (B') layer Adhesion method in which hot-melt powder, adhesive, etc. is applied by spray type, roll type, etc., and bonded by heat treatment, etc.; , an adhesive sheet method in which a sheet-like material such as a photomelt film or a mesh is interposed for adhesion, and a method in which a tucker or a nail is driven in to fix the adhesive sheet. The bond may be adhered at multiple points.

Subsequently, (B''2) an air layer is formed between the surfaces of the (B') layer to which the (B) air-permeable resin foam layer is not adhered (C). A breathable resin layer is laminated.
As means for laminating the (B') layer and the (C) low-permeability resin layer so that (B''2) an air layer is formed between them, there is a method of partially heat-bonding, as well as a method of bonding. Examples include a method of partially laminating and integrating via an agent, but the layer (B') and the low-permeability resin layer (C) may be simply superimposed and laminated without using an adhesive. . Each lamination method can be performed in the same manner as the method for laminating the above-described (B) breathable resin foam layer and (B') layer.

In this embodiment, when two or more fiber layers are stacked as the (B') layer, the individual fiber layers may be sequentially stacked, or two or more fiber layers may be stacked simultaneously.

The multilayer sound absorbing material of this embodiment is used with the (C) low-permeability resin layer side positioned on the sound incident side. (C) By locating the low-permeability resin layer side on the sound incident side, the sound absorption performance can be effectively improved.

In the multilayer sound absorbing material of the present embodiment, (B) the air-permeable resin foam layer alone has low sound absorption performance in the entire frequency range, and the higher the frequency, the higher the sound absorption coefficient tends to be, but (A) low air permeability Resin layer, (B) air-permeable resin foam layer, (B''1) air layer, (B') layer, (B''2) air layer, and (C) low air-permeability resin layer are laminated in this order. With this configuration, the sound absorption coefficient in the low frequency range of 500 to 2000 Hz increases, and it is possible to express particularly high sound absorption in the vicinity of 1000 Hz. Noise can be suppressed.
In addition, in the second aspect of the multilayer sound absorbing material of the present embodiment, the layer (B') and the air layer (B''2) are further provided on the sound source side of the (B) breathable resin foam layer. Therefore, compared with the first aspect of the multilayer sound absorbing material of the present embodiment described above, it is possible to exhibit even higher sound absorbing performance.
FIG. 5 shows the relationship between the frequency and the reverberant room sound absorption coefficient in the example described later.

In the second aspect of the multilayer sound absorbing material of the present embodiment, the sound absorption coefficient at 1000 Hz is preferably within the range described above.
The sound absorption coefficient can be measured by the method described in Examples below.

In addition, the multilayer sound absorbing material of the present embodiment has (C) a low-permeability resin layer on the outermost surface on the sound source side, (A) a low-permeability resin layer on the outermost surface on the side opposite to the sound source, and further (B ) With the configuration in which (B''1) air layer, (B') layer, and (B''2) air layer are provided on the sound source side of the air-permeable resin foam layer, in the entire frequency range It can demonstrate sound insulation performance that surpasses existing sound absorbing materials.
In addition, in the second aspect of the multilayer sound absorbing material of the present embodiment, the layer (B') and the air layer (B''2) are further provided on the sound source side of the (B) breathable resin foam layer. As a result, even higher sound insulation performance can be exhibited compared to the first aspect of the multilayer sound absorbing material of the present embodiment described above.
FIG. 6 shows the relationship between frequency and sound transmission loss in the example described later.

In the second aspect of the multilayer sound absorbing material of the present embodiment, the transmission loss at 1000 Hz is preferably within the range described above.
The transmission loss can be measured by the method described in Examples below.

A second aspect of the multilayer sound absorbing material of the present embodiment can be used as a member that shields various noises, such as a sound insulating member in an engine room of a vehicle such as an automobile. In particular, by selecting a hard thermoplastic resin for the (B) air-permeable resin foam layer, a self-supporting sound absorbing body that can stand on its own with only the multilayer sound absorbing material of this embodiment without further laminating other members. can be used.

A third aspect of the multilayer sound absorbing material of the present embodiment is (A) a low-permeability resin layer having a thickness of 0.5 to 10 mm, and (B) an air-permeable resin foam layer having a porosity of 15 to 97%. , the surface opposite to the (A) low-permeability resin layer side has a plurality of recessed holes, and the thickness (L) of the portion other than the portion provided with the recessed holes is 2 to 80 mm, and the recessed A breathable resin foam layer having a pore depth of 30 to 95% of the thickness (L) and an aperture ratio of 20 to 90%, (B''1) air having a thickness of 0.01 to 2.0 mm Layer, (B′) layer having a thickness (t′) of 0.1 to 4 mm containing a fiber aggregate having an air permeability of 2 to 70 cc/(cm ² ·sec), (B″2) thickness of 0.01 to An air layer of 2.0 mm and (C) a low-permeability resin layer with a thickness (t) of 0.05 to 3.0 mm and a ventilation resistance of 20 kN s/m3 ^or more are laminated in this order. Characterized by

The multilayer sound absorbing material of the present embodiment includes the above (A) low-permeability resin layer, (B) air-permeable resin foam layer, (B''1) air layer, (B') layer, (B''2) ) air layer and (C) low-permeability resin layer, other layers described above may be included. In addition, in order to impart design properties, a resin layer having a mirror surface or textured surface may be provided on the outermost surface.
Among them, the multilayer sound absorbing material is composed of (A) a low-permeability resin layer, (B) a permeable resin foam layer, (B''1) an air layer, (B') a layer, ( It is preferable to consist only of B''2) an air layer and (C) a low-permeability resin layer.
FIG. 4C is a schematic cross-sectional view of a third aspect of the multilayer sound absorbing material of this embodiment.

In the third aspect of the multilayer sound absorbing material of the present embodiment, the thickness of the multilayer sound absorbing material is preferably within the range described above.

((A) Low air permeability resin layer)
In the third aspect of the multilayer sound absorbing material of the present embodiment, the (A) low-permeability resin layer described above can be used as the (A) low-permeability resin layer.

((B) Breathable resin foam layer)
In the third aspect of the multilayer sound absorbing material of the present embodiment, the (B) air-permeable resin foam layer has a porosity of 15 to 97%, and (A) the side opposite to the low-permeability resin layer side ((B ''1) It has a plurality of concave holes on the surface (air layer side), the thickness (L) of the part other than the part where the concave holes are provided is 2 to 80 mm, and the depth of the concave holes is the above It is 30 to 95% of the thickness (L) and has an aperture ratio of 20 to 90%.

(B) In the breathable resin foam layer, the thickness (L) of the portion other than the portion provided with the recessed holes is 2 to 80 mm, and 3 to 50 mm, from the viewpoint of achieving both sound absorption and thickness reduction. It is preferably 5 to 20 mm, more preferably 5 to 20 mm.

Regarding the three-dimensional shape of the recess, the shape and area of the cross section perpendicular to the depth direction may be constant or variable in the depth direction. A shape in which the concave holes are continuously connected inside may be used.
The opening shape of the concave hole is not particularly limited, and examples thereof include a circular shape, an elliptical shape, and a polygonal shape. The opening shape of each concave hole may be the same or different.

The number of concave holes and the opening area of each concave hole are not particularly limited as long as the opening ratio of the (B) breathable resin foam layer is 20 to 90%. It is preferably 100 cm ² , more preferably 0.03 to 50 cm ² and even more preferably 0.05 to 30 cm ² .
The opening area of each concave hole is the area of each concave hole on the surface of the (B) air-permeable resin foam layer opposite to the (A) low-permeability resin layer side ((B''1) air layer side). Refers to the area of the opening.
In addition, the arrangement of the concave holes on the surface of the (B) air-permeable resin foam layer opposite to the (A) low-permeability resin layer side ((B''1) air layer side) is determined by the opening area density (unit area It is preferable that the opening area per unit area) is uniform, but they do not necessarily need to be arranged periodically, and may be arranged randomly.

In the (B) air-permeable resin foam layer, the depth of the pits is determined from the viewpoint of sound insulation performance in the low frequency range of 500 to 2000 Hz. It is 30 to 95%, preferably 35 to 90%, more preferably 40 to 85% of the thickness (L) of the portion other than the portion. If the depth of the pits is less than 30%, the sound insulation performance tends to be insufficient in the low frequency range of 500 to 2000 Hz. There is a tendency for non-uniform filling to occur, resulting in poor appearance.
It should be noted that the depth of the concave hole refers to the average value of the depths of the plurality of concave holes.

(B) The permeable resin foam layer has an open area ratio of 20 to 90%, preferably 30 to 85%, more preferably 40 to 80%. If the aperture ratio is less than 20%, the sound insulation performance tends to be insufficient in the low frequency range of 500 to 2000 Hz, and if the aperture ratio exceeds 90%, the mechanical strength tends to decrease. tend to become
The open area ratio of the (B) air-permeable resin foam layer is the total open area of the recesses with respect to the total area of the surface of the (B) air-permeable resin foam layer opposite to the (A) low-permeability resin layer side. It refers to the ratio of and is represented by the following formula (I).
Aperture ratio = (total opening area of each concave hole) x 100/{(total opening area of each concave hole) + ((B) air-permeable resin foam layer opposite to (A) low air-permeable resin layer side the area of the portion of the side surface other than the portion provided with the concave hole)} (I)

(B) The breathable resin foam layer is preferably a molded body in which resin foam particles having concave structures are fused to each other, and may have continuous voids between the fused resin foam particles. preferable. That is, the (B) breathable resin foam layer of the present embodiment is preferably a molded body having at least a portion in which at least two or more resin foam particles are fused together. There are fused parts and voids between the fused resin foam particles.
Moreover, the molded article is preferably a molded article obtained by fusion molding resin foam particles.
That is, for the (B) breathable resin foam layer, the same resin foam as the (B) breathable resin foam layer of the above first and second aspects can be used. In the (B) air-permeable resin foam layer of the second embodiment, the depth of the recesses is equal to the thickness ( It is possible to use one provided with a plurality of concave holes that are 50% or more of L).
(B) The porosity and fusion bond strength of the air-permeable resin foam layer are preferably within the ranges described above.
The porosity and fusion bonding strength can be measured by the methods described in Examples below.

The method of forming the concave holes is not particularly limited. For example, when molding the resin foam, the concave holes may be formed by using a mold having concave holes formed in advance, or by cutting with a mill or the like. may be formed.

((B''1) air layer and (B''2) air layer)
In the third aspect of the multilayer sound absorbing material of the present embodiment, (B''1) air layer and (B''2) air layer are respectively the (B''1) air layer and (B''2) It can be formed in the same manner as the air layer. The preferable range of thickness is also the range described above.
Note that (B''1) the thickness of the air layer is calculated without including the inner space of the recesses even in the portions corresponding to the recesses provided in the (B) breathable resin foam layer. and

((C) Low air permeability resin layer)
In the third aspect of the multilayer sound absorbing material of the present embodiment, the (C) low-permeability resin layer described above can be used as the (C) low-permeability resin layer.

((B') layer)
In the third aspect of the multilayer sound absorbing material of the present embodiment, the layer (B') described above can be used as the layer (B').

In the third aspect of the multilayer sound absorbing material of the present embodiment, (A) a low-permeability resin layer, (B) an air-permeable resin foam layer, (B''1) an air layer, (B') a layer, (B ''2) The lamination system of the air layer and (C) the low-permeability resin layer can use the lamination system in the above-described second aspect.

The multilayer sound absorbing material of this embodiment is used with the (C) low-permeability resin layer side positioned on the sound incident side. (C) By locating the low-permeability resin layer side on the sound incident side, the sound absorption performance can be effectively improved.

In the multilayer sound absorbing material of the present embodiment, (B) the air-permeable resin foam layer alone has low sound absorption performance in the entire frequency range, and the higher the frequency, the higher the sound absorption coefficient tends to be, but (A) low air permeability Resin layer, (B) air-permeable resin foam layer, (B''1) air layer, (B') layer, (B''2) air layer, and (C) low air-permeability resin layer are laminated in this order. With this configuration, the sound absorption coefficient in the low frequency range of 500 to 2000 Hz increases, and it is possible to express particularly high sound absorption in the vicinity of 1000 Hz. Noise can be suppressed.
In addition, in the third aspect of the multilayer sound absorbing material of the present embodiment, the layer (B') and the air layer (B''2) are further provided on the sound source side of the (B) breathable resin foam layer. Therefore, compared with the first aspect of the multilayer sound absorbing material of the present embodiment described above, it is possible to exhibit even higher sound absorbing performance.

In the third aspect of the multilayer sound absorbing material of the present embodiment, the sound absorption coefficient at 1000 Hz is preferably within the range described above.
The sound absorption coefficient can be measured by the method described in Examples below.

In addition, the multilayer sound absorbing material of the present embodiment has (C) a low-permeability resin layer on the outermost surface on the sound source side, (A) a low-permeability resin layer on the outermost surface on the side opposite to the sound source, and further (B ) With the configuration in which (B''1) air layer, (B') layer, and (B''2) air layer are provided on the sound source side of the air-permeable resin foam layer, in the entire frequency range It can demonstrate sound insulation performance that surpasses existing sound absorbing materials.
In addition, in the third aspect of the multilayer sound absorbing material of the present embodiment, the layer (B') and the air layer (B''2) are further provided on the sound source side of the (B) breathable resin foam layer. As a result, even higher sound insulation performance can be exhibited compared to the first aspect of the multilayer sound absorbing material of the present embodiment described above.

In the third aspect of the multilayer sound absorbing material of the present embodiment, the transmission loss at 1000 Hz is preferably within the range described above.
The transmission loss can be measured by the method described in Examples below.

A third aspect of the multi-layered sound absorbing material of the present embodiment can be used as a member for shielding various noises, such as a sound insulating member in an engine compartment of a vehicle such as an automobile. In particular, by selecting a hard thermoplastic resin for the (B) air-permeable resin foam layer, a self-supporting sound absorbing body that can stand on its own with only the multilayer sound absorbing material of this embodiment without further laminating other members. can be used.

The embodiments of the present invention are illustrated by the following examples. However, the scope of the present invention is not limited by the examples.

Evaluation methods used in Examples and Comparative Examples are described below.

(1) Airflow resistance (kN·s/m ³ ) of (A) low air permeability resin layer and (C) low air permeability resin layer
The AC method of the international standard ISO9053 was applied, and the flow resistance measurement system AirReSys type manufactured by Nippon Onkyo Engineering Co., Ltd. was used for measurement. That is, using the film-shaped resin layer samples (A) and (C), the differential pressure P (Pa) between the front and back surfaces of the material is measured in a uniform flow at a flow rate of F = 0.5 mm / s, It was obtained as P/F (kN·s/m ³ ) from the differential pressure. When a high resistance exceeding 20 kN·s/m ³ was shown, it was described as “>20 kN·s/m ³ ”.

(2) Resin density ρ ₀ (g/cm ³ )
After measuring the mass W (g) of the resin before foaming, the volume V (cm ³ ) was measured by the submersion method, and W/V (g/cm ³ ) was defined as the density of the resin.

(3) True density ρ ₁ (g/cm ³ ) of foamed resin particles
After measuring the mass W (g) of the expanded resin beads, the volume V (cm ³ ) was measured by the submersion method, and W/V (g/cm ³ ) was taken as the true density of the expanded resin beads.
The density of the resin raw material pellets after pre-foaming was measured with a hydrometer.

(4) Bulk Density ρ ₂ (g/cm ³ ) of Expanded Resin Particles
Bulk volume V ₁ (cm ³ ) as a value obtained by reading the scale on the flattened upper surface when 100 g of resin foamed particles were placed in a graduated cylinder and vibrated, and the volume reached a constant weight, and the mass of the graduated cylinder containing the resin foamed particles. W ₁ (g) and the mass W ₀ (g) of the graduated cylinder were measured and obtained by the following formula.
ρ ₂ = [W ₁ -W ₀ ]/V ₁

(5) Average particle diameter (mm) of expanded resin particles
100 g of foamed resin particles are specified by JIS Z8801, and the nominal dimensions are d ₁ = 5.6 mm, d ₂ = 4.75 mm, d ₃ = 4 mm, d ₄ = 3.35 mm, d ₅ = 2.36 mm, d Classification is carried out using standard sieves with ₆ = 1.7 mm, _d = _1.4 mm, d = 1 mm, X _i the weight fraction of particles passing through sieve d _i and stopping on sieve d _i+1 , total The average particle diameter D of the particle aggregate was determined by the following formula.
D=ΣX _i (d _i ·d _i+1 ) ^1/2
(i represents an integer from 1 to 7)

(6) (B) Porosity (%) of breathable resin foam layer
The porosity of the (B) air-permeable resin foam layer was obtained from the following formula.
(B) Porosity (%) of breathable resin foam layer = [(B−C)/B]×100
However, B: (B) the apparent volume (cm ³ ) of the air-permeable resin foam layer, C: (B) the true volume (cm ³ ) of the air-permeable resin foam layer, and the apparent volume is (B) the air permeability The volume calculated from the external dimensions of the breathable resin foam layer and the true volume C mean the actual volume of the (B) breathable resin foam layer excluding voids. The true volume C is obtained by measuring the volume gained when the (B) breathable resin foam layer is submerged in a liquid (eg, alcohol).

(7) Presence or Absence of Continuous Gaps Judgment was made as follows from the measurement of the unit length flow resistance.
As a method for measuring the unit length flow resistance value, the AC method of the international standard ISO9053 was applied and the flow resistance measurement system AirReSys type manufactured by Nippon Onkyo Engineering Co., Ltd. was used. That is, using a flat resin foam molded product sample with a thickness of 10 mm, the differential pressure P (Pa) between the front and back surfaces of the material is measured in a uniform flow at a flow rate of F = 0.5 mm / s. It was obtained from the material thickness t (m) as P/(t·F) (N·s/m ⁴ ). When the unit length flow resistance value is 200,000 N·s/m ⁴ or less, it is evaluated as having continuous voids (○), and when it exceeds 200,000 N·s/m ⁴ , it is evaluated as having no continuous voids (×). did.

(8) (B) Fusion Strength of Breathable Resin Foam Layer Tensile strength was measured based on JIS K6767A. When the breaking elongation was 1% or more and less than 2%, the fusion bonding strength was evaluated as good (◯), and when the breaking elongation was less than 1%, the fusion bonding strength was evaluated as poor (×).

(9) Fabric weight of fiber assembly (g/m ² )
The mass per unit area (ISO method) of JIS L-1913 "Testing methods for general nonwoven fabrics" was evaluated according to the described method, and the basis weight of the fiber assembly was determined.

(10) Average apparent density of fiber assembly (g/cm ³ )
The average thickness is evaluated according to the method described in JIS L-1913 "General nonwoven fabric test method" for thickness (ISO method), and from the basis weight of the fiber assembly in (8) above, (average apparent density of the fiber assembly) = (weight of fiber assembly)/(thickness).

(11) Average fiber diameter (μm) of fiber assembly
A 500-fold enlarged photograph was taken with a microscope, and the average diameter of 30 randomly selected fibers was obtained.

(12) Air permeability of fiber assembly (cc/(cm ² ·sec))
Measured according to the method described in JIS L-1096 "Testing methods for woven and knitted fabrics".

(13) Sound Absorption Properties of Multilayer Sound Absorbing Material Sound absorption coefficient was measured at an air temperature of 25° C. by the reverberation chamber method using AbLoss, a sound transmission loss/reverberation chamber method sound absorption coefficient measurement system manufactured by Nihon Onkyo Engineering Co., Ltd. A sample having a size of 1000 mm×1000 mm was prepared from the multilayer sound absorbing material, and the sample was left standing so that the low-permeability resin layer (A) side was in contact with the floor surface and measured. 1/3 octave centered at 500Hz, 630Hz, 800Hz, 1000Hz, 1250Hz, 1600Hz, and 2000Hz. When the number of frequencies with a ratio of 0.27 or more is more than 6 points, the sound absorption characteristics are particularly excellent (*), when the score is 5 to 6 points, the sound absorption characteristics are excellent (◎), and when the frequency ratio is 3 to 4 points, the sound absorption characteristics are good ( ○), and a case of 2 points or less was evaluated as poor sound absorbing property (x).

(14) Sound Insulation Properties of Multi-Layer Sound Absorbing Material Transmission loss was measured at a temperature of 25° C. by the anechoic chamber/reverberant chamber method using a sound absorption coefficient measurement system AbLoss manufactured by Nihon Onkyo Engineering Co., Ltd. A sample of 600 mm x 600 mm size was prepared from multilayer sound absorbing material, and the effective measurement surface was set to 500 mm x 500 mm. It was installed and the transmission loss (dB) was measured. According to the measurement results, among the average transmission loss of 1/3 octave and 7 bands with 7 points of 500Hz, 630Hz, 800Hz, 1000Hz, 1250Hz, 1600Hz and 2000Hz as the center frequency, the number of frequencies with a transmission loss of 12dB or more is more than 6 points. A score of 5 to 6 indicates excellent sound insulation (*), a score of 3 to 4 indicates good sound insulation (○), and a score of 2 or less indicates poor sound insulation. It was evaluated as inferior (x). Furthermore, of the 1/3 octave with four center frequencies of 1000 Hz, 1250 Hz, 1600 Hz, and 2000 Hz, and the average transmission loss of the four bands, the frequency band with a transmission loss of 16 dB or more is four points in the 1000 to 2000 Hz region. Excellent sound insulation characteristics (*), 3 points indicate excellent sound insulation characteristics in the same frequency range (◎), 2 points indicate good sound insulation characteristics in the same frequency range (○), and 1 point or less indicate the same It was evaluated as poor (x) in sound insulation properties in the frequency range.

(15) Autonomy (Flexibility)
A 30 cm square multi-layer sound absorbing flat plate sample was held horizontally by a cantilever, and the amount of deflection was evaluated. A sample in which a clear deflection of about 1 cm or more occurred was evaluated as inferior (×), and a sample in which a clear deflection of about 1 cm or more was not observed was evaluated as good (◯).

(A) Low air permeability resin layer (A-1) Polyamide 6 (thickness: 1 mm, ventilation resistance: >20 kN s/m ³ ) (manufactured by Toray Plastics Seiko)
(A-2) Polyamide 6 (thickness: 2 mm, ventilation resistance: >20 kN s/m ³ (manufactured by Toray Plastics Seiko)
(A-3) Polyethylene terephthalate (thickness: 1 mm, ventilation resistance: >20 kN s/m ³ (manufactured by Toray Plastics Seiko)

(B) Breathable resin foam layer (molded body)
(B-1)
Polyamide 6 resin (UBE nylon "1022B", manufactured by Ube Industries, surface tension 46 mN / m at 20 ° C.) was melted using an extruder and extruded from a profile extrusion die having a cross-sectional shape shown in Fig. 3 (a1). The strand was pelletized with a pelletizer to obtain pellets with an average particle size of 1.4 mm. The obtained pellets were put into a pressure cooker at 10° C., and carbon dioxide gas of 4 MPa was blown thereinto for absorption for 3 hours. Next, the mini-pellets impregnated with carbon dioxide gas were transferred to a foaming device, and air at 240° C. was blown for 20 seconds to obtain aggregates of foamed polyamide resin particles. The average particle diameter of the expanded polyamide resin particles contained in the obtained aggregate of expanded polyamide resin particles was 2.0 mm. When the expanded polyamide resin beads were cut and observed, it was found that a large number of closed cells were evenly formed on the cut surface of the expanded polyamide resin beads. The cross section of the foamed polyamide resin beads had a concave structure in the shape shown in FIG. 3(a2).
The polyamide resin foamed particle aggregate thus obtained was placed in the pressure cooker again and allowed to absorb 4 MPa of carbon dioxide gas at 10° C. for 3 hours. Next, the polyamide resin foamed particles impregnated with carbon dioxide gas are filled in a mold of an in-mold foam molding device, and air at 230° C. is blown in for 30 seconds to form a molded article (B-1) in which the polyamide resin foamed particles are fused together. got The expansion ratio of the molding was 7.5 times. When the molded article was cut and observed, it was found that an aggregate of polyamide resin expanded particles having a large number of closed cells with a cell diameter of 200 to 400 μm was formed. It was confirmed from the measurement value of airflow resistance that it had continuous voids.
Table 1 shows the evaluation results of the foamed resin particles and molded articles.
(B-2) to (B-5), (B-7)
Molded articles (B-2) to (B-2) under the same conditions as molded article (B-1) except that the cross-sectional shape and average particle diameter of the expanded particles, the thickness of the molded article and the porosity of the molded article were as shown in Table 1. (B-5) and (B-7) were obtained.
Table 1 shows the evaluation results of the foamed resin particles and molded articles.
(B-6)
Using a copolyester-based resin as the resin species, resin foamed particles and molded articles were produced as follows.
100 parts by mass of a polycondensate of ethylene glycol, isophthalic acid, and terephthalic acid (isophthalic acid content: 2% by mass, surface tension: 43 mN/m at 20°C), 0.3 parts by mass of pyromellitic dianhydride, and carbonic acid A mixture with 0.03 parts by mass of sodium is melted and kneaded at 270 to 290° C. by an extruder, while butane as a foaming agent is injected in the middle of the barrel at a rate of 1.0% by mass with respect to the mixture. After pre-foaming through a profile extrusion die having the cross-sectional shape described in a1), the resin foam was immediately cooled in a cooling water bath and cut into small particles using a pelletizer to produce foamed resin particles. The cross-sectional shape of the obtained expanded resin beads was shown in FIG. 3(a2). Further, the bulk density ρ ₂ of the obtained resin expanded beads was 0.14 g/cm ³ and the average particle diameter was 1.5 mm.
The foamed resin particles are placed in a closed container, carbon dioxide gas is injected at a pressure of 0.49 MPa, and the mixture is held for 4 hours. The mold is clamped, water vapor at a gauge pressure of 0.02 MPa is introduced into the mold for 10 seconds, and then water vapor at a gauge pressure of 0.06 MPa is introduced into the mold for 20 seconds. A molded product (B-6) was obtained. The expansion ratio of the molding was 4.6 times. It was confirmed from the measurement value of airflow resistance that it had continuous voids.
Table 1 shows the evaluation results of the foamed resin particles and molded articles.

(C) Low air permeability resin layer (C-1) Polyamide 6 (thickness: 0.2 mm, ventilation resistance: >20 kN s/m ³ ) (manufactured by Toray Plastics Seiko Co., Ltd., polyamide N6)
(C-2) Polypropylene (thickness: 0.075 mm) (Torayfan, manufactured by Toray Industries) is provided with a plurality of through-holes having a diameter of 0.5 mm to adjust the ventilation resistance to 2 kN·s/m ³ .
(C-3) Polyethylene terephthalate (thickness: 0.1 mm, ventilation resistance: >20 kN s/m ³ ) (manufactured by Toray, Lumirror)
(C-4) A film obtained by providing a plurality of through holes with a diameter of 0.5 mm in a polypropylene (thickness: 0.03 mm) (Torayfan, manufactured by Toray Industries, Inc.) and adjusting the ventilation resistance to 1 kN·s/m ³ .

Fiber layer (F-1) constituting the fiber assembly of the (B') layer
Polyethylene terephthalate (1% using orthochlorophenol, solution viscosity η _sp /c 0.77 at 25°C method, melting point 263°C) was spunbonded using a spinneret at a spinning temperature of 300°C to capture a fiber web. Polyethylene terephthalate (solution viscosity η _sp /c 0.50, melting point 260° C. by 25° C. method) is applied to the continuous long fiber web (basis weight 45 g/m ² , average fiber diameter 14 μm) through a melt blow nozzle. The yarn was directly spouted at a spinning temperature of 300° C. and heated air of 320° C. at 1000 Nm 2 /hr to form an ultrafine fiber web (weight per unit area: 10 g/m ² , average fiber diameter: 2 μm). Furthermore, a composite long fiber web (basis weight: 45 g/m 2 ) consisting of high-density polyethylene (melting point: 130°C) and polyethylene terephthalate (melting point: 263°C) is applied to the ultrafine fiber web using a bicomponent spinneret ^. , average fiber diameter 18 μm) is partially thermocompressed with a pair of embossing roll/flat roll temperature 230 ° C./flat roll temperature 230 ° C./105 ° C., linear pressure 300 N / cm, basis weight 100 g / m ² , average apparent density 0.25 g /cm ³ , an average fiber diameter of 14 μm, and a thickness of 0.4 mm.
(F-2)
Polyethylene terephthalate (1% using orthochlorophenol, solution viscosity η _sp /c 0.77 at 25°C method, melting point 263°C) was spunbonded using a spinneret at a spinning temperature of 300°C to capture a fiber web. Formed on a collection net, polyethylene terephthalate (solution viscosity η _sp /c 0.50 by 25 ° C. method, melting point 260 ° C.) was added to the continuous long fiber web (basis weight 22.5 g / m ² , average fiber diameter 14 μm). Using a melt blow nozzle, the yarn was directly blown out at a spinning temperature of 300° C. and heated air of 320° C. at 1000 Nm ² /hr to form an ultrafine fiber web (weight per unit area: 10 g/m ² , average fiber diameter: 2 μm). Furthermore, a composite long fiber web (basis weight: 22.5 g) was formed on the ultrafine fiber web using a two-component spinneret, the sheath component being a copolymer polyester resin (melting point: 130°C) and the core component being polyethylene terephthalate (melting point: 263°C). /m ² , average fiber diameter 18 μm) was partially thermocompressed with a pair of embossed rolls/flat rolls at a temperature of 230° C./145° C. and a linear pressure of 300 N/cm to obtain a basis weight of 55 g/m ² and an average apparent density of A fiber assembly (F-2) having a weight of 0.25 g/cm ³ , an average fiber diameter of 13.5 μm, a thickness of 0.25 mm and a thermocompression rate of 20% was obtained.
(G-1)
Polyethylene terephthalate (1% using orthochlorophenol, solution viscosity η _sp /c 0.77 at 25°C method, melting point 263°C) was spunbonded using a spinneret at a spinning temperature of 300°C to capture a fiber web. Formed on a collection net, the continuous filament web (weight per unit area: 100 g/m ² , average fiber diameter: 14 μm) was rolled to obtain a weight per unit area of 400 g/m ² , an average apparent density of 0.23 g/cm ³ , an average fiber diameter of 14 μm, A fiber assembly (felt) (G-1) having a thickness of 0.5 mm and a thermocompression rate of 15% was obtained.

[Example 1]
As shown in Table 2, (A) as a low-permeability resin layer (A-1), (B) as a permeable resin foam layer (B-1), (C) as a low-permeability resin layer (C-1 )It was used. (A-1), (B-1), and (C-1) are set to overlap in this order from the bottom, and (B'') air between (B-1) and (C-1) The tension of each layer was adjusted so that the layers were formed, and the layers were fixed with a tucker at a fixed density on square lattice points with a period of 20 cm to obtain a multilayer sound absorbing material.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the evaluation results.

[Examples 2 to 5, 11]
(A) low-permeability resin layer, (B) air-permeable resin foam layer, (B'') air layer, and (C) low-permeability resin layer were configured as shown in Table 2, except that A multilayer sound absorbing material was obtained in the same manner as in Example 1.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the evaluation results.

[Example 6]
As shown in Table 2, (A) as a low-permeability resin layer (A-1), (B) as a permeable resin foam layer (B-1), (C) as a low-permeability resin layer (C-1 )It was used. As the (B') layer, a fiber assembly obtained by stacking six nonwoven fabrics (F-1) and needle-punching them at a punch density of 50 fibers/cm ² was used. (A-1), (B-1), the fiber assembly, and (C-1) are set so as to overlap in this order from the bottom, and between (B-1) and the fiber assembly (B'' 1) Adjust the arrangement so that an air layer (B''2) air layer is formed between the fiber assembly and (C-1), respectively, and fix only the periphery with a tucker, A multilayer sound absorbing material was obtained.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the evaluation results.

[Examples 7 to 10]
(A) low air permeability resin layer, (B) air permeability resin foam layer, (B''1) air layer, (B') layer, (B''2) air layer, (C) low air permeability resin A multilayer sound absorbing material was obtained in the same manner as in Example 6, except that the layers were configured as shown in Table 2.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the evaluation results.

5 is a graph showing the relationship between the frequency and the sound absorption coefficient of Examples 1 and 6, and FIG. 6 is a graph showing the relationship between the frequency and the transmission loss rate.

[Example 12]
(A) low-permeability resin layer of (B) air-permeable resin foam layer by imparting convex shapes periodically arranged to one mold surface during molding of (B) air-permeable resin foam layer A multilayer sound absorbing material was obtained by applying the same manufacturing method as in Example 6 except that concave holes were periodically formed on the surface of the opposite side ((B''1) air layer side).
(B) The shape of the concave holes in the breathable resin foam layer has an average depth of 5 mm (the ratio of the average depth to the thickness (L) is 63%), and the shape of the cross section perpendicular to the depth direction is (B). The air-permeable resin foam layer surface side is a circle with an average diameter of 28 mm, and the inner side (bottom side) is a circular truncated cone with an average diameter of 15 mm. did. The aperture ratio was 68%.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the evaluation results.
Compared with Example 6, it can be seen that the sound insulation performance is improved particularly in the 1 to 2 kHz range.

[Example 13]
(A) low-permeability resin layer of (B) air-permeable resin foam layer by imparting convex shapes periodically arranged to one mold surface during molding of (B) air-permeable resin foam layer A multilayer sound absorbing material was obtained by applying the same manufacturing method as in Example 7 except that concave holes were periodically formed on the surface of the opposite side ((B''1) air layer side).
(B) The shape of the concave holes in the breathable resin foam layer has an average depth of 14 mm (the ratio of the average depth to the thickness (L) is 74%), and the shape of the cross section perpendicular to the depth direction is (B). The air-permeable resin foam layer has a circle with an average diameter of 28 mm on the surface side and a circular truncated cone with an average diameter of 13 mm on the inner side (bottom side). It was made as follows. The aperture ratio was 57%.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the evaluation results.
Compared to Example 7, it can be seen that the sound insulation performance is improved particularly in the 1 to 2 kHz range.

[Example 14]
(B) The surface of the air-permeable resin foam layer on the side opposite to the (A) low-permeability resin layer side ((B''1) air layer side) is formed with periodically arranged concave holes by cutting. A multilayer sound absorbing material was obtained by applying the same manufacturing method as in Example 7, except for the above.
(B) The shape of the concave holes in the breathable resin foam layer has an average depth of 12 mm (the ratio of the average depth to the thickness (L) is 63%), and the shape of the cross section perpendicular to the depth direction is (B). The air-permeable resin foam layer surface side is a square with an average side of 28 mm, and the inner side (bottom side) is a square pyramid with an average side of 40 mm. It was made as follows. The aperture ratio was 64%.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the evaluation results.
Compared to Example 7, it can be seen that the sound insulation performance is improved particularly in the 1 to 2 kHz range.

5 is a graph showing the relationship between the frequency and the sound absorption coefficient of Example 12, and FIG. 6 is a graph showing the relationship between the frequency and the transmission loss factor.

[Comparative Examples 1 and 3]
(A) low-permeability resin layer, (B) air-permeable resin foam layer, (B'') air layer, and (C) low-permeability resin layer were configured as shown in Table 2, except that A multilayer sound absorbing material was obtained in the same manner as in Example 1. The sound absorbing properties, sound insulation properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the evaluation results.

[Comparative Example 2]
A multi-layered sound absorbing material composed only of (A) a low-permeability resin layer and (B) a permeable resin foam layer was obtained.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the results.

[Comparative Examples 4 to 6]
(A) low air permeability resin layer, (B) air permeability resin foam layer, (B''1) air layer, (B') layer, (B''2) air layer, (C) low air permeability resin A multilayer sound absorbing material was obtained in the same manner as in Example 6, except that the layers were configured as shown in Table 2.
The sound absorbing properties, sound insulating properties, and self-sustainability of the multilayer sound absorbing material were evaluated by the methods described in Evaluation Methods (13) to (15). Table 2 shows the results.

5 is a graph showing the relationship between frequency and sound absorption coefficient of Comparative Examples 1 and 2, and FIG. 6 is a graph showing the relationship between frequency and transmission loss.

All of Examples 1 to 14 showed high absorption and insulation performance in the frequency range of 500 to 2000 Hz even though they were thin, and exhibited characteristics as a self-supporting sound absorbing material that exhibits particularly good sound absorption and insulation performance around 1 kHz. .
On the other hand, from the results of Comparative Examples 1 to 6, it can be seen that when the requirements of the present invention are not satisfied, either the sound absorption and insulation performance is inferior in the frequency range of 500 to 2000 Hz, or the sound insulation is not self-sustaining.

The multilayer sound absorbing material of the present embodiment is a self-supporting multilayer sound absorbing material that has high sound absorption and insulation performance in the low frequency range of 500 to 2000 Hz, especially in the low frequency range of around 1000 Hz, even if it is thin. etc. can be effectively reduced.
Examples of applications of the multilayer sound absorbing material of this embodiment include members used to reduce driving noise of vehicles such as automobiles, trains, and trains, and aircraft, etc., which require light weight and noise reduction. It can be particularly suitably used for engine covers, engine capsules, engine room hoods, transmission casings, sound absorbing covers, motor casings for electric vehicles, sound absorbing covers, etc. in automobile engine rooms that require deformability and heat insulation.
Furthermore, the multi-layered sound absorbing material of this embodiment can be used for air conditioning equipment such as air conditioners, refrigerators, heat pumps, etc., parts that form air passages such as ducts, washing machines, dryers, refrigerators, vacuum cleaners, etc. where noise reduction is required. It can be suitably used for various household electric appliances, printers, copiers, OA equipment such as facsimiles, as well as building materials such as core materials for wall materials and core materials for floor materials.

1: (A) Low air permeability resin layer 2: (B) Air permeability resin foam layer 3: (B'') Air layer 3a: (B''1) Air layer 3b: (B''2) Air layer 4: (C) low air permeability resin layer 5: (B') layer 6: concave hole

Claims (7)

(A) a low-permeability resin layer with a thickness of 0.5 to 10 mm, (B) a breathable resin foam layer with a thickness (L) of 2 to 80 mm and a porosity of 15 to 97%, (B'') a thickness of 0 An air layer of 0.01 to 2.0 mm and (C) a low-permeability resin layer with a thickness (t) of 0.05 to 3.0 mm and a ventilation resistance of 20 kN s/m3 ^or more are laminated in this order. A multi-layered sound absorbing material characterized by comprising: (A) Low air permeability resin layer with a thickness of 0.5 to 10 mm, (B) Air permeability resin foam layer with a thickness (L) of 2 to 80 mm and a porosity of 15 to 97%, (B''1) Thickness An air layer of 0.01 to 2.0 mm, (B') a layer having a thickness (t') of 0.1 to 4 mm containing a fiber aggregate having an air permeability of 2 to 70 cc/(cm ² ·sec), (B ''2) An air layer with a thickness of 0.01 to 2.0 mm, and (C) a low-permeability resin layer with a thickness (t) of 0.05 to 3.0 mm and a ventilation resistance of 20 kN s/m3 or ^more . , is laminated in this order. (A) a low-permeability resin layer having a thickness of 0.5 to 10 mm; (B) a permeable resin foam layer having a porosity of 15 to 97%; has a plurality of concave holes on its surface, the thickness (L) of the part other than the part where the concave holes are provided is 2 to 80 mm, and the depth of the concave holes is 30 to 95 of the thickness (L) % and an open area ratio of 20 to 90%, (B''1) an air layer having a thickness of 0.01 to 2.0 mm, and (B') an air permeability of 2 to 70 cc/( cm ² sec) layer with a thickness (t′) of 0.1 to 4 mm containing a fiber aggregate, (B″2) an air layer with a thickness of 0.01 to 2.0 mm, and (C) airflow resistance A multilayer sound absorbing material characterized by laminating low-permeability resin layers having a thickness (t) of 0.05 to 3.0 mm and a thickness (t) of 20 kN·s/m ³ or more in this order. 2. The air-permeable resin foam layer (B) is a molded body in which resin foam particles having concave structures are fused to each other, and has continuous voids between the fused resin foam particles. 4. The multilayer sound absorbing material according to any one of -3. The fiber aggregate has a basis weight of 100 to 1000 g/m ² , an average apparent density of 0.10 to 1.0 g/cm ³ , and an average fiber diameter of 0.6 to 50 μm,
4. The multilayer sound absorbing material according to claim 2 or 3 , having a thickness of 3 to 80 mm. The (B) breathable resin foam layer contains a resin having a surface tension of 37 to 60 mN/m at 20°C, or a resin having a glass transition temperature of -10°C or higher and 280°C or lower. 6. The multilayer sound absorbing material according to any one of 5. The multilayer sound absorbing material according to any one of claims 1 to 6, which is a self-supporting sound absorbing body.

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