JP6904445B2 - Flame-retardant sound absorbing material - Google Patents

Description

The present invention relates to a flame-retardant sound absorbing material that absorbs noise from home appliances and the like and also has flame retardancy.

Conventionally, it is known that a sound absorbing material is used in home appliances such as electric refrigerators, air conditioners, and vacuum cleaners in order to absorb noise and vibration generated by motors, compressors, and the like. Sound absorbing materials for such applications are also required to have excellent flame retardancy, assuming ignition using a motor, compressor, or the like as a heat generating source.
For example, Patent Document 1 describes flame retardancy in which fiber entangled portions are not fused and integrated by being made of a specific polyester fiber containing a flame retardant such as a phosphorus compound and manufactured by a needle punch method or the like. A non-woven sound absorbing sheet material is disclosed.

Japanese Unexamined Patent Publication No. 2006-144160

However, according to the study of the present inventor, the flame-retardant non-woven fabric sound-absorbing sheet material of Patent Document 1 has insufficient sound-absorbing property.

An object of the present invention is to provide a flame-retardant sound-absorbing material having excellent sound-absorbing properties and flame-retardant properties and suppressing the falling off of the contained flame retardant agent particles.

The present invention has the following configurations.
[1] A flame-retardant sound absorbing material composed of a middle layer and a surface layer provided on at least one surface of the middle layer.
The surface layer is made of a porous sheet having a flame retardant particle content of 10% by mass or less and a flame retardant property of UL94 of HF-1 or more.
The middle layer contains flame retardant particles, a raw material fiber (a) containing 40% by mass or more of a fiber (α) having at least one of a hollow tubular shape and a crimped shape, and a heat-sealing fiber (b). A flame-retardant sound-absorbing material, which comprises an air-laid non-woven fabric formed by using the material.
[2] The flame-retardant sound absorbing material according to [1], wherein the Frazier air permeability according to JIS-L1096: 1998 is 5 to 100 ^{cm 3} / cm ² · s ^-1.
[3] A flame-retardant sound absorbing material comprising a middle layer, a surface layer provided on one surface of the middle layer, and a rubber layer provided on the other surface of the middle layer.
The surface layer is made of a porous sheet having a flame retardant particle content of 10% by mass or less and a flame retardant property of UL94 of HF-1 or more.
The middle layer contains flame retardant particles, a raw material fiber (a) containing 40% by mass or more of a fiber (α) having at least one of a hollow tubular shape and a crimped shape, and a heat-sealing fiber (b). A flame-retardant sound-absorbing material, which comprises an air-laid non-woven fabric formed by using the material.
[4] The flame-retardant sound absorbing material according to [3], further comprising a surface layer between the middle layer and the rubber layer.
[5] The flame-retardant sound absorbing material according to [3] or [4], wherein the Frazier air permeability according to JIS-L1096: 1998 is 5 to 100 ^{cm 3} / cm ² · s ^{-1 in the portion other than the rubber layer.} ..
[6] The flame-retardant sound absorbing material according to any one of [1] to [5], wherein the fiber (α) contains pulp fiber.
[7] The flame-retardant sound-absorbing material according to any one of [1] to [6], wherein the ratio of the thickness of the middle layer to the thickness of the flame-retardant sound-absorbing material is 70 to 99.8%.
[8] The flame-retardant sound absorbing material according to any one of [1] to [7], wherein the content of the raw material fiber (a) in the middle layer is 20 to 70% by mass.

According to the present invention, it is an object of the present invention to provide a flame-retardant sound-absorbing material which is excellent in sound absorption and flame retardancy and in which the fall of the contained flame retardant particles is suppressed.

Hereinafter, the present invention will be described in detail.
"First embodiment"
The flame-retardant sound-absorbing material of the first embodiment of the present invention is a sheet-shaped flame-retardant sound-absorbing material composed of a middle layer and a surface layer provided on at least one surface of the middle layer.

[Middle layer]
The middle layer uses flame retardant particles, a raw material fiber (a) containing 40% by mass or more of a fiber (α) having at least one of a hollow tubular shape and a crimped shape, and a heat-sealing fiber (b). It consists of an air-laid non-woven fabric formed in the above. The flame retardant particles are components that impart flame retardancy to the middle layer, and the raw material fiber (a) is a component that is responsible for sound absorption. Further, the heat-sealing fiber (b) is a binder component for joining the raw material fibers (a) to each other and fixing the flame retardant particles between the raw material fibers (a).

The air-laid non-woven fabric is a non-woven fabric in which a web is formed by an air-laid method in which fibers constituting the non-woven fabric are three-dimensionally and randomly laminated by using an air flow.
At the time of laminating the raw material fiber (a) and the heat-sealing fiber (b), flame retardant particles are also added to form a web by the airlaid method, and then heat treatment is performed to obtain heat-sealing property with the raw material fiber (a). The fibers (b) and the flame retardant particles are adhered at points to obtain an air-laid nonwoven fabric in which the flame retardant particles are dispersed and retained between the fibers. In such an air-laid non-woven fabric, the raw material fiber (a) responsible for sound absorption exists in a relatively free state, and is excellent in sound absorption and also excellent flame retardancy due to flame retardant particles. Here, if flame retardancy is imparted to the air-laid non-woven fabric by a method of impregnating the flame retardant aqueous solution in which the flame retardant is dissolved and then drying, or a method of spraying the flame retardant aqueous solution with a spray or the like and then drying, the raw material is used. The degree of freedom of the fiber (a) is reduced, and the voids between the fibers are blocked by the flame retardant. Therefore, although excellent flame retardancy can be obtained, sound absorption is lowered.

(Flame retardant particles)
The flame retardant particles are particulate and retained in the middle layer. Examples of the flame retardant particles include flame retardant particles such as halogen bromine type, hydrated metal type, antimony oxide type, phosphorus type, and phosphorus / nitrogen type condensate, and one or more of these can be used. Among them, the flame retardant particles are phosphorus-nitrogen type because they are excellent in the effect of imparting flame retardancy to the middle layer formed by containing the raw material fibers (a) and the heat-sealing fibers (b). Flame retardant particles containing a condensate are preferred. The flame retardant particles containing a phosphorus / nitrogen-based condensate have char formation by flame heat, surface coating of the raw material fiber (a) by phosphorus melting, formation of foamed char, radical trap in the gas phase, and oxygen dilution by nitrogen gas. Etc. and exhibit flame retardancy.
Examples of the flame retardant particles containing a phosphorus-nitrogen condensate include "Non-Nen R028-1" manufactured by Maruhishi Yuka Kogyo.

The particle size of the flame retardant particles is not particularly limited, but the average particle size is preferably in the range of 10 to 500 μm, more preferably in the range of 30 to 100 μm. When the average particle size is within the above range, the flame retardant particles are less likely to fall off from the middle layer and are easily held stably.
In the present specification, the average particle size is a value measured by a laser diffraction / scattering type particle size distribution measuring device (LA-910 manufactured by HORIBA).

(Raw material fiber (a))
The raw material fiber (a) contains 40% by mass or more of the fiber (α) having at least one of the hollow tubular and crimped forms. The fiber having a hollow tubular form is a fiber having a hollow portion along the axial direction. A fiber having a crimp-like morphology is a fiber in which at least a part of the fiber is curved or bent by crimp, curl, spiral or the like. The bending and bending may or may not have regularity.
It is considered that the fiber having a hollow tubular shape attenuates noise and vibration by having a hollow portion (void) and exhibits excellent sound absorption. It is considered that the fibers having a crimped shape exhibit excellent sound absorption because the fibers are easily entangled with each other and voids are easily formed between the fibers.

From the viewpoint of sound absorption, the raw material fiber (a) preferably contains the fiber (α) in an amount of 40% by mass or more and is preferably 60% by mass or more. The raw material fiber (a) may be composed of only the fiber (α). That is, the raw material fiber (a) may contain 100% by mass of the fiber (α). Further, the raw material fiber (a) may contain, as other fibers, other fibers made of natural fibers or synthetic resins, which are neither hollow tubular nor crimped, in the range of 60% by mass or less, and when included, the raw material fibers (a) may contain. It is preferably contained in the range of 40% by mass or less.

The fiber (α) is not limited in its material as long as it has at least one of a hollow tubular shape and a crimped shape, and may be a natural fiber or a fiber made of a synthetic resin. One or more kinds of fibers (α) can be used.

Examples of natural fibers include pulp fibers.
Pulp fibers are fibers having an irregularly bent shape and a crimp-like morphology, and also fibers having a hollow tubular morphology having pores (lumens) occupied by the protoplasm of plant cells. is there. As an index showing the shape characteristics of the pulp fiber, the curl index indicated by (actual fiber length-distance between both ends) / (distance between both ends) of the pulp fiber and (fiber wall thickness x 2) / (lumen diameter) are indicated. The runkel ratio is known. When the pulp fiber is a chemical pulp, it may have a flat shape with crushed lumens depending on the chemical treatment method, tree species, etc., but it can be used as a fiber (α) without any problem.

Pulp fibers include wood pulp (coniferous tree pulp, broadleaf tree pulp), rug pulp, linter pulp, linen pulp, non-wood pulp such as 楮, sansho, and ganpi pulp, and pulp such as used paper pulp; these pulps are used as raw material pulps. Fluff pulp in which raw material pulp is defibrated into fibers by mechanical treatment; Of these, fluff pulp is preferable because it has excellent sound absorption. Among the fluff pulps, fluff pulp using softwood pulp as a raw material pulp is preferable from the viewpoint that an air-laid non-woven fabric having excellent strength can be easily obtained.

The method for pulping the raw material pulp is not particularly limited, and those obtained by a known method can be used.
Generally, the water content of the raw material pulp before fluffing is 35% by mass or less, preferably 10% by mass or less, and about 2% by mass or more. By defibrating the raw material pulp in a dry state having a low water content, it is difficult to bond between the fibers, and a pulp itself which is bulky can be efficiently obtained.
The non-woven fabric produced by using such fluff pulp tends to have gaps inside, reduce the density, and have excellent sound absorption.

There is no particular limitation on the equipment used when defibrating the raw pulp by mechanical treatment, but for example, a known defibrator used when manufacturing absorbent materials such as paper diapers, frictional force as mechanical treatment, etc. A defibrator or the like that utilizes shearing force can be preferably used. Specifically, a defibrator having a toothed cylinder can be preferably used (see Japanese Patent No. 2521577).
The shape of the raw material pulp to be used for mechanical treatment is not particularly limited, but sheet-shaped pulp (so-called pulp sheet) or sheet-shaped pulp that has been squeezed into a form like a take-up roll is easy to handle. Therefore, it is preferable.

Examples of the fiber made of synthetic resin include polyester such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), nylon (registered trademark), polyethylene (PE), polypropylene (PP), polylactic acid (PLA) and the like. There are no restrictions on the type of synthetic resin as long as it has at least one of the hollow tubular and crimped forms, including fibers. However, when fibers made of synthetic resin are used, in the heat treatment for adhering the raw material fibers (a) and the flame retardant particles by melting the heat-sealing fibers (b) during the manufacturing process of the middle layer, Use one that does not melt.

As a fiber made of a synthetic resin and having a hollow tubular form, for example, a method of stretching a hollow tubular fiber precursor made of a thermoplastic resin to reduce the diameter; fibers having different components at least in the central portion and the outer peripheral portion. Examples thereof include those produced by a method of producing a precursor and removing the central component from the fiber precursor by dissolving or the like to form a hollow tubular shape; or the like. As the fiber having a hollow tubular shape, a fiber produced by any method can be used. The hollow ratio of the fiber having a hollow tubular shape is also not particularly limited.

Commercially available fibers having a hollow tubular shape include, for example, Teijin Fiber's hollow polyester fiber "Aerocapsule", Asahi Kasei's polyester fiber "Twin Air", Toray's hollow nylon fiber "Farillo", and Daiwa Bow Rayon's. Examples include the flat hollow rayon fiber "Corona SBH" and the polylactic acid fiber "HP8F" manufactured by Unitica.

As the fiber made of synthetic fiber and having a crimp-like morphology, a fiber obtained by applying crimp to a non-crimp fiber by an artificial method can be used.
As a method of imparting crimp to the fiber, a method by an external force such as a false twisting process or a semi-stretching method in which a part of the fiber is stretched; a composite manufactured by laminating multiple kinds of materials having different coefficients of thermal expansion. Examples thereof include a method of crimping the fiber by performing a heat treatment. Although it does not originally have crimping, latent crimped fibers that are crimped by heat treatment or the like during the production of the middle layer can also be used.
Composite fibers include side-by-side type, core-sheath type, sea-island type, and multi-layer type. Examples of the combination of a plurality of types of materials having different thermal expansion rates include PET / PET, PE / PE, PP / PP, PE / PET, PP / PET, PE / PP and the like.

Commercially available fibers having a crimp-like morphology include, for example, latent crimp polyester fiber "C81" made by Unitica, polylactic acid fiber "Teramac" made by Unitica, and polyester-based two-component composite synthetic fiber made by Kuraray. Examples thereof include latent crimp fiber "Microcrimp" and bulky fiber "Miracle Fiber CQ-V" which is a polyester / polyolefin composite type synthetic fiber manufactured by Daiwa Bow Polytech.

The fineness of the fiber (α) made of the synthetic resin is preferably 0.01 to 22 dtex, more preferably 1 to 12 dtex. When the fineness is not less than the lower limit value of the above range, the flame retardant particles are likely to be stably held in the middle layer, and when it is not more than the upper limit value, the sound absorption property of the flame retardant sound absorbing material tends to be excellent.
The length of the fiber (α) made of synthetic resin The weighted average fiber length is that when the web is formed by the airlaid method, the fibers are three-dimensionally randomly laminated, have an appropriate density, and have excellent sound absorption. From the viewpoint that a non-woven fabric can be easily obtained, the thickness is preferably 1 to 30 mm, more preferably 2 to 15 mm. When the length-weighted average fiber length is less than the lower limit value or exceeds the upper limit value in the above range, the fibers are difficult to stack three-dimensionally and tend to be oriented two-dimensionally.
When the raw material fiber (a) contains other fibers made of natural fibers or synthetic resins that are neither hollow tubular nor crimped, the fineness and length-weighted average fiber length of the fibers are also within the above ranges. It is preferable to have.

The fiber (α) preferably has a crimped shape and a hollow tubular shape from the viewpoint of sound absorption, and may contain pulp fiber from the viewpoint of industriality such as cost. It is preferable that the pulp fiber in the fiber (α) is contained in an amount of 50% by mass or more, and it is particularly preferable that the pulp fiber is contained only.

(Heat-fused fiber (b))
At least a part of the heat-sealing fiber (b) is melted by heat treatment when producing the air-laid non-woven fabric forming the middle layer, and acts as a binder. As the heat-sealing fiber (b), a heat-sealing fiber having a core-sheath structure or the like, which is obtained by synthesizing two kinds of resins having different melting points and in which the fiber is partially melted, is preferable. The heat-sealing fiber having a core-sheath structure has a structure in which a sheath made of a resin having a low melting point is formed on the outer periphery of a core made of a resin having a high melting point. Examples thereof include forms in which the above resins are combined (PET / PET composite fiber, PE / PE composite fiber, PP / PP composite fiber, PE / PET composite fiber, PP / PET composite fiber, PE / PP composite fiber).

Commercially available products of the heat-sealing fiber (b) include, for example, a two-component composite synthetic fiber (“ESC871” manufactured by ES Fiber Vision, PE / PP, length-weighted average fiber length 5 mm, fineness 1.7 dtex). Two-component composite synthetic fiber (Unitica fiber "Melty 4080Wet", PET / PET, length-weighted average fiber length 5 mm, fineness 2.2 dtex), two-component composite synthetic fiber (Unitica "Casben # 7080", PET / PET, fineness 2.2 dtex, length-weighted average fiber length 5 mm) and the like. When higher flame retardancy is required, "Melty 7080 Wet" having a high LOI value is preferable. The LOI value is a numerical value used as a scale for measuring flame retardancy, and is defined by the critical oxygen index of JIS K7201.

The fineness of the heat-sealing fiber (b) is preferably 0.01 to 22 dtex, more preferably 1 to 12 dtex. If the fineness is not less than the lower limit of the above range, a bulky and thick air-laid non-woven fabric can be obtained, and if it is not more than the upper limit, the number of contacts between fibers is likely to increase. can do.
The length-weighted average fiber length of the heat-fusing fiber (b) is such that when the web is formed by the air-laid method, the fibers are three-dimensionally randomly laminated, have an appropriate density, and have excellent sound absorption. From the viewpoint that a non-woven fabric can be easily obtained, the thickness is preferably 1 to 30 mm, more preferably 2 to 15 mm. When the length-weighted average fiber length is less than the lower limit value or exceeds the upper limit value in the above range, the fibers are difficult to stack three-dimensionally and tend to be oriented two-dimensionally.

(Content, thickness, basis weight of each component in the middle layer)
The content of the flame retardant particles in the middle layer is preferably 10 to 50% by mass, more preferably 15 to 30% by mass, still more preferably 15 to 25% by mass, when the mass of the middle layer is 100% by mass. When the content of the flame retardant particles is at least the lower limit of the above range, the flame retardancy of the flame retardant sound absorbing material is more excellent. When it is not more than the upper limit of the above range, the flame retardant particles are hard to fall off from the middle layer and are easily held stably, and the ratios of the raw material fibers (a) and the heat-sealing fibers (b) are relatively increased. The sound absorption of the flame retardant sound absorbing material and the strength of the middle layer tend to be excellent.
The content of the raw material fiber (a) in the middle layer is preferably 20 to 70% by mass, more preferably 50 to 70% by mass, still more preferably 55 to 65% by mass, assuming that the mass of the middle layer is 100% by mass. When the content of the raw material fiber (a) is at least the lower limit of the above range, the sound absorbing property of the flame-retardant sound absorbing material is excellent. When it is not more than the upper limit of the above range, the ratio of the heat-sealing fiber (b) and the flame retardant particles is relatively increased, and the flame retardancy of the flame retardant sound absorbing material and the strength of the middle layer tend to be excellent.
The content of the heat-sealing fiber (b) in the middle layer is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and 15 to 25% by mass when the mass of the middle layer is 100% by mass. More preferred. When the content of the heat-sealing fiber (b) is at least the lower limit of the above range, the strength of the middle layer is excellent. When it is not more than the upper limit of the above range, the ratio of the raw material fiber (a) and the flame retardant particles is relatively increased, and the sound absorbing property and the flame retardant property of the flame retardant sound absorbing material tend to be excellent.

When the thickness of the flame-retardant sound absorbing material is 100%, the ratio of the thickness of the middle layer is preferably 70.0 to 99.8%, more preferably 75.0 to 99.0%. When the ratio of the thickness of the middle layer is within the above range, the sound absorbing property of the flame-retardant sound absorbing material can be sufficiently obtained.
The thickness of the middle layer is preferably 2 to 50 mm, more preferably 4 to 40 mm. When the thickness of the middle layer is at least the lower limit of the above range, the sound absorbing property of the flame-retardant sound absorbing material can be sufficiently obtained. When it is not more than the upper limit of the above range, the flame-retardant sound absorbing material can be made compact.

The basis weight of the middle layer is preferably ^{100~3000g / m 2, 450~2000g / m} 2 is more preferable. When the basis weight of the middle layer is not less than the lower limit of the above range, a flame-retardant sound absorbing material having excellent sound absorption can be obtained, and when it is not more than the upper limit of the above range, it is compact and has excellent mountability. It can be a sex sound absorbing material.

[Surface layer]
The surface layer is a layer provided on at least one surface of the middle layer, and is made of a porous sheet having a flame retardancy of UL94 of HF-1 or higher. When the flame retardancy of the porous sheet by UL94 is HF-1 or higher, the flame retardancy of the flame-retardant sound absorbing material as a whole is excellent. Further, by using a porous sheet for the surface layer, noise and vibration are not reflected by the surface layer, and noise and vibration can be reliably attenuated in the middle layer. The porous sheet is a sheet having a large number of fine pores penetrating the front and back surfaces, which will be described in detail later.
Further, the surface layer has an effect of preventing the flame retardant particles contained in the middle layer from falling off to the outside of the flame retardant sound absorbing material (also referred to as “powder falling”). From the viewpoint of effectively preventing powder from falling off, the surface layer is preferably provided on both sides of the middle layer. For example, the flame-retardant sound absorbing material is installed so as to be wound directly around an object such as a home appliance. In some cases, it is not necessary to provide a surface layer made of a porous sheet on the surface on the side in contact with the object. That is, whether the surface layer is provided on one surface of the middle layer or on both sides can be appropriately selected depending on the usage conditions, usage mode, and the like of the flame-retardant sound absorbing material. Further, when it is sufficient to give sound absorption to only one surface of the flame-retardant sound absorbing material, a surface layer made of the above-mentioned porous sheet is provided on the one surface, and UL94 is provided on the other surface. A non-porous sheet having a flame retardancy of HF-1 or higher may be provided.

The porous sheet includes fibers made of natural fibers (for example, pulp fibers, etc.), synthetic resins (for example, polyesters such as PET and PBT), non-woven fabrics and woven fabrics manufactured using fibers such as glass fibers. , Knitted fabric; Inorganic fiber paper; etc., and resin sheets having a large number of fine holes formed therein.
As the porous sheet, a sheet having pores of an appropriate size is selected according to the particle size of the flame retardant particles so that the powder of the flame retardant particles contained in the middle layer can be suppressed from falling off. For example, in the case of a non-woven fabric, the size of the pores can be adjusted by adjusting the manufacturing method of the non-woven fabric, the fineness of the fibers used, and the like.

The porous sheet may be one with a flame retardant or one without a flame retardant as long as the flame retardancy by UL94 is HF-1 or higher.

As a method of applying the flame retardant, a method of impregnating the porous sheet in the flame retardant aqueous solution in which the flame retardant is dissolved and then drying; Method of spraying with a spray, etc .; Method of adding a flame retardant by kneading a flame retardant into the components used for manufacturing the porous sheet in advance; Using flame retardant particles during the manufacture of the porous sheet, the porous sheet , Etc., and one or more of these methods can be adopted.
Examples of the precursor of the porous sheet include a web formed by the airlaid method and in which fibers are not yet bonded to each other.
As a method of using flame retardant particles in the production of the porous sheet and containing the flame retardant particles in the porous sheet, it is difficult to make the air-laid non-woven fabric by using the flame retardant particles together with the fibers when forming the web by the air-laid method. Examples thereof include a method of containing flame retardant particles.

However, when the porous sheet contains flame retardant particles, if the content of the flame retardant particles in 100% by mass of the porous sheet exceeds 10% by mass, the flame retardant particles will fall off from the porous sheet. It can be noticeable. Therefore, when the porous sheet contains the flame retardant particles, the content of the flame retardant particles in 100% by mass of the porous sheet is 10% by mass or less. It is preferably 5% by mass or less, and more preferably 0% by mass (the porous sheet does not contain flame retardant particles).
When the porous sheet contains particles other than the flame retardant particles (for example, colorant particles, conductive particles, etc.), the total content of the flame retardant particles and the particles other than the flame retardant particles. However, it is preferably 10% by mass or less, and more preferably 5% by mass or less, based on 100% by mass of the porous sheet.

Examples of the porous sheet capable of exhibiting a flame retardancy of UL94 of HF-1 or higher even when a flame retardant is not applied include fiber sheets such as woven fabrics and non-woven fabrics using glass fibers.

As the porous sheet used for the surface layer, non-woven fabrics such as air-laid non-woven fabric and melt-blown non-woven fabric to which flame retardant is imparted by using an aqueous flame retardant solution; flame retardant particles are contained in a range of 10% by mass or less, and it is difficult. Air-laid non-woven fabrics to which flame retardancy has been imparted using an aqueous solution of a flame retardant; glass cloth to which no flame retardant has been imparted; and the like are preferable. When flame retardant is imparted to a non-woven fabric such as air-laid non-woven fabric or melt blown non-woven fabric by using an aqueous flame retardant solution, the flame retardant covers a part or all of the fibers constituting the non-woven fabric, or the flame retardant is amoeba in the non-woven fabric. It becomes a state that exists like a state. Here, "exists like an amoeba" means that a flame retardant having a plurality of thread-like protrusions extending in irregular directions exists between the fibers constituting the non-woven fabric.
In particular, when the cost of the flame retardant sound absorbing material is emphasized, a flame retardant aqueous solution and, if necessary, flame retardant particles are used in an air-laid non-woven fabric containing pulp fiber as a main component (containing more than 50% by mass). A porous sheet to which flame retardancy has been imparted is preferable, and when higher sound absorption is important, a melt blown non-woven fabric to which flame retardancy has been imparted by using an aqueous flame retardant is preferable. The melt-blown non-woven fabric is considered to have excellent sound absorption due to the thin fibers constituting the non-woven fabric.

When the air-laid non-woven fabric is adopted, the fineness and length-weighted average fiber length of the fibers constituting the air-laid non-woven fabric are within the same range as the fineness and length-weighted average fiber length described for the fiber (α) used in the middle layer. Is preferable.
As the flame retardant particles, for example, the flame retardant particles exemplified in the description of the middle layer can be used.
As the flame retardant aqueous solution, for example, an aqueous solution of a guanidine phosphate-based flame retardant, an aqueous solution of guanyl urea phosphate, an aqueous solution of guanidine sulfamate, or the like can be used.

The thickness of the surface layer is not particularly limited, but is preferably 0.01 to 2.0 mm, more preferably 0.05 to 1.0 mm. When the thickness of the surface layer is at least the lower limit of the above range, it is possible to more effectively prevent the flame retardant particles contained in the middle layer from falling off. When it is not more than the upper limit of the above range, the flame-retardant sound absorbing material can be made compact.
The basis weight of the surface layer is not particularly limited but is preferably ^{10~100g / m 2, 20~60g / m} 2 is more preferable. When the basis weight of the surface layer is at least the lower limit of the above range, it is possible to more effectively prevent the powder of the flame retardant particles contained in the middle layer from falling off. If it is not more than the upper limit of the above range, the flame-retardant sound absorbing material can be made compact.

[Flame-retardant sound absorbing material]
The flame-retardant sound absorbing material according to the first embodiment of the present invention preferably has a Frazier air permeability according to JIS-L1096: 1998 of 5 to 100 ^{cm 3} / cm ² · s ^-1 , preferably 5 to 60 ^{cm 3} / cm ^{2. -S-1} is more preferable, and 5 to ³⁰ cm 3 / cm ² · s- ¹ is particularly preferable. When the Frazier air permeability is within the above range, noise and vibration from the object pass through the surface layer and are effectively attenuated in the middle layer, so that the sound absorption is excellent. The Frazier air permeability of the flame-retardant sound absorbing material tends to depend mainly on the composition of the surface layer. Therefore, by appropriately selecting the porous sheet used for the surface layer, the Frazier air permeability of the flame-retardant sound absorbing material can be adjusted within the above range. In order to keep the Frazier air permeability of the flame-retardant sound absorbing material within the above range, it is preferable that ^{the Frazier air permeability of the porous sheet constituting the surface layer alone is 5 to 500 cm 3} / cm ² · s ^-1. 5 to 200 ^{cm 3} / cm ² · s ^-1 is more preferable, and 10 to 30 cm ³ / cm ² · s ^-1 is particularly preferable.

The thickness of the flame-retardant sound absorbing material as a whole is preferably 3 to 50 mm, more preferably 5 to 20 mm.
The basis weight of the flame-retardant sound absorbing material as a whole is preferably 100 to 5000 g / m ^{2 and} more preferably ^{200 to 2000 g / m 2 from the viewpoint of achieving both sound absorption and mountability.}

A flame-retardant sound absorbing material having a three-layer structure having surface layers on both sides of the middle layer can be produced as follows.
First, a porous sheet constituting the surface layer is fed out on a mesh conveyor having a suction box, and a powder adhesive is sprayed on the porous sheet. Then, the raw material fibers (a) constituting the middle layer, the heat-sealing fibers (b), and the flame retardant particles are uniformly mixed and defibrated in the air, and a porous sheet is used using a dry air-laid web forming apparatus. On top of this, an air-laid web that constitutes the middle layer is formed.
Then, a powder adhesive is sprayed on the air-laid web, and a porous sheet is fed onto the air-laid web so as to be laminated, and guided to a hot air dryer to at least a part of the heat-sealing fibers (b). Melts and heats above the temperature at which it acts as a binder.
As a result, the flame retardant particles are fixed in the air-laid web, and the porous sheets are adhered to both sides of the air-laid web to form a laminated body (hereinafter, also referred to as “laminated body S”).
Then, the laminate S is further passed through a press roll and molded to have a desired basis weight, thickness, and apparent density, whereby a middle layer is formed between the surface layer (I) and the surface layer (II). A flame-retardant sound absorbing material having a three-layer structure can be obtained.
The powder adhesive is an adhesive used for bonding the surface layer (I) to the middle layer and the middle layer to the surface layer (II), and is, for example, PE, PP, PET, ethylene / acetic acid. A powder made of a vinyl copolymer (EVA) or the like can be used.

A two-layer flame-retardant sound absorbing material having a surface layer on one surface of the middle layer can be produced as follows.
First, a porous sheet constituting the surface layer is fed out on a mesh conveyor having a suction box, and a powder adhesive is sprayed on the porous sheet. Then, the raw material fibers (a) constituting the middle layer, the heat-sealing fibers (b), and the flame retardant particles are uniformly mixed and defibrated in the air, and a porous sheet is used using a dry air-laid web forming apparatus. On top of this, an air-laid web that constitutes the middle layer is formed.
Then, the carrier sheets were fed out on the air-laid web so as to be laminated without spraying the powder adhesive, and guided to a hot air dryer to melt at least a part of the heat-sealing fibers (b), and the binder was used. Heat above the temperature at which it acts.
As a result, the flame retardant particles are adhered to the air-laid web, the porous sheet is adhered to one surface of the air-laid web, and the carrier sheet is arranged on the other surface (hereinafter, "laminate S'"). Also called).
After that, the laminate S'is further passed through a press roll, molded to have a desired basis weight, thickness, and apparent density, and then the carrier sheet is peeled off to make it difficult to form a two-layer structure of a surface layer and a middle layer. A flammable sound absorbing material can be obtained.

As described above, the flame retardant sound absorbing material of the first embodiment of the present invention has a flame retardant particle content of 10% by mass or less as a surface layer and a flame retardant property of UL94 of HF. Raw material fiber (a) having -1 or more porous sheets, while containing 40% by mass or more of flame retardant particles and fibers (α) having at least one of hollow tubular and crimped forms as a middle layer. And an air-laid non-woven fabric formed by using the heat-sealing fiber (b). Therefore, the flame-retardant sound-absorbing material according to the first embodiment of the present invention is excellent in sound-absorbing property and flame-retardant property, and the fall of the flame retardant particles contained therein is also suppressed.
That is, by using the air-laid non-woven fabric as the middle layer, the flame retardant particles, the raw material fibers (a), and the heat-sealing fibers (b) can be adhered at points, and the flame retardant particles can be dispersed and held between the fibers. Therefore, the raw material fiber (a) responsible for sound absorption exists in a relatively free state, and a middle layer having excellent sound absorption and excellent flame retardancy due to the flame retardant particles can be formed. Further, since the heat-sealing fiber (b) adheres and holds the flame retardant particles, it is possible to prevent the flame retardant particles from falling off.
Further, since such a middle layer contains particulate flame retardant particles as a flame retardant, there is a concern that the flame retardant particles may fall off. However, the flame retardant sound absorbing material of the first embodiment of the present invention has a flame retardant sound absorbing material. Since it has a surface layer, it is possible to prevent the flame retardant particles contained in the middle layer from falling to the outside.
Further, since the surface layer contains 10% by mass or less of the flame retardant particles, powder falling from the surface layer is also suppressed. Further, since the surface layer is formed of a sheet having a flame retardancy of HF-1 or higher due to UL94, the flame retardancy of the flame-retardant sound absorbing material as a whole can also be achieved to be HF-1 or higher. Further, since the sheet forming the surface layer is a porous sheet, it can be effectively attenuated in the middle layer without reflecting noise and vibration from home appliances and the like.

The flame-retardant sound-absorbing material according to the first embodiment of the present invention is usually incorporated in a home electric appliance and used in a form of being wound or attached to a motor, a compressor, or the like. Not limited to.

"Second embodiment"
The flame-retardant sound absorbing material of the second embodiment of the present invention comprises a middle layer, a surface layer (I) provided on one surface of the middle layer, and a rubber layer provided on the other surface of the middle layer. It is a sheet-shaped flame-retardant sound absorbing material provided. That is, the flame-retardant sound absorbing material of the second embodiment of the present invention is a laminated body in which at least a middle layer and a surface layer (I) are laminated in this order on a rubber layer, and the middle layer and the rubber layer are combined with each other. A surface layer (II) may be further provided between them. Specific forms of this laminated body include, for example, (1) and (2) shown below.
(1): A laminate in which at least a rubber layer, a surface layer (II), a middle layer, and a surface layer (I) are laminated in this order, that is, a laminated body having surface layers on both sides of the middle layer and a middle layer of one surface layer. A layered laminate having a rubber layer on the surface opposite to the surface. The rubber layer is arranged directly on the main surface of the surface layer (II) or adjacent to the surface layer (II) via an adhesive layer.
(2): A laminated body in which at least a rubber layer, a middle layer, and a surface layer (I) are laminated in this order, that is, a layer having a surface layer on one surface of the middle layer and a rubber layer on the other surface of the middle layer. Laminate of composition. The rubber layer is arranged directly on the main surface of the middle layer or adjacent to each other via another layer.

Examples of the other layer in the form (2) mentioned above include an adhesive layer and a tissue layer.

The middle layer and each surface layer (surface layer (I) and surface layer (II)) in the flame-retardant sound absorbing material of the second embodiment of the present invention are the same as the middle layer and the surface layer in the first embodiment. Since the preferred conditions and the like are the same, the description thereof will be omitted.

[Rubber layer]
Examples of the rubber constituting the rubber layer include natural rubber and synthetic rubber.
Examples of synthetic rubber include ethylene / propylene / diene rubber (EPDM), isobutylene / isoprene rubber (IIR), acrylonitrile / butadiene rubber (NBR), chloroprene rubber (CR), styrene / butadiene rubber (SBR), and silicone rubber (SR). , Urethane rubber, fluororubber, etc., and one or more of these can be used. Of these, EPDM, IIR, or a combination thereof is preferable.

The rubber layer may contain an arbitrary component other than the rubber component.
Optional components include inorganic fillers such as black fillers (carbon black, etc.) and white fillers (barium sulfate, etc.); organic fillers such as phenol resins and styrene resins; non-reinforcing fillers such as calcium carbonate. Can be mentioned.

The thickness of the rubber layer is preferably 0.5 mm or more from the viewpoint of imparting not only sound absorption but also sound insulation to the flame-retardant sound absorbing material. Further, the thickness of the rubber layer is more preferably 0.5 to 3.0 mm, preferably 1.0 to 2.5 mm, from the viewpoint of not only imparting the sound absorbing property and sound insulating property but also being easy to perform processing such as cutting. More preferred.

The density of the rubber layer is preferably ^{1.0 g / cm 3} or more from the viewpoint of imparting not only sound absorption but also sound insulation to the flame-retardant sound absorbing material. Further, the density of the rubber layer is more preferably 1.0 to 5.0 ^{g / cm 3} , and 1.5 to 3 from the viewpoint that not only the sound absorbing property and the sound insulating property are imparted but also processing such as cutting is easy. .0 g / cm ³ is even more preferred.

[Flame-retardant sound absorbing material]
In the flame-retardant sound absorbing material of the second embodiment of the present invention, the portion of the flame-retardant sound absorbing material excluding the rubber layer preferably has a Frazier air permeability according to JIS-L1096: 1998 of 5 to 100 ^{cm 3} / cm ² · s ^-1 . 5 to 60 ^{cm 3} / cm ² · s ^-1 is more preferable, and 5 to ³⁰ cm 3 / cm ² · s ^-1 is particularly preferable. When the Frazier air permeability is within the above range, noise and vibration from the object pass through the surface layer (I) and are effectively attenuated in the middle layer, so that the sound absorption is excellent. The Frazier air permeability of the flame-retardant sound absorbing material tends to depend mainly on the composition of each surface layer. Therefore, by appropriately selecting the porous sheet used for each surface layer, the Frazier air permeability of the flame-retardant sound absorbing material can be adjusted within the above range. In order to keep the Frazier air permeability of the flame-retardant sound absorbing material within the above range, it is preferable that ^{the Frazier air permeability of the porous sheet alone constituting each surface layer is 5 to 500 cm 3} / cm ² · s ^-1. , 5 to 200 ^{cm 3} / cm ² · s ^-1 is more preferable, and 10 to 30 cm ³ / cm ² · s ^-1 is particularly preferable. In particular, the Frazier air permeability of the porous sheet alone constituting the surface layer (I) is preferably within the above range.

The thickness of the flame-retardant sound absorbing material as a whole is preferably 3 to 55 mm, more preferably 5 to 25 mm.
The basis weight of the whole flame retardant sound absorbing material, from the viewpoint of compatibility of the sound absorbing property and mounting property, preferably 100~7000g / ^{m 2,} more preferably ^{200~5000g / m 2, 300~3000g / m} 2 and more preferable.

A laminate in which at least the rubber layer, the surface layer (II), the middle layer, and the surface layer (I) are laminated in this order can be produced, for example, as follows.
First, in the same manner as in the first embodiment, surface layers are adhered to both sides of the middle layer to form a laminated body S, and the laminated body S is passed through a press roll so as to obtain a desired basis weight, thickness, and apparent density. To obtain a laminated body T.
Then, an adhesive is applied to one surface of the sheet-shaped rubber layer to form an adhesive layer. The laminate T is laminated on the adhesive layer so that one surface layer to be the surface layer (II) of the laminate T and the adhesive layer are adjacent to each other.
Then, the rubber layer, the surface layer (II), the middle layer, and the surface layer (I) are laminated in this order by performing a press punching process using a punching die according to the use of the flame-retardant sound absorbing material. As a body, a flame-retardant sound absorbing material having a layer structure in which the rubber layer is adjacently arranged on the main surface of the surface layer (II) via an adhesive layer can be obtained.
Even if an adhesive is applied to the surface of the laminated body T on the side opposite to the middle layer of one of the surface layers (II) to form an adhesive layer, and a rubber layer is laminated on the adhesive layer. Good.

The adhesive is used for adhering the surface layer (II) to the rubber layer and forms an adhesive layer. As the adhesive, for example, a solid hot melt adhesive, a solution (latex emulsion) adhesive, or the like can be used. Further, the surface layer (II) and the rubber layer may be bonded to each other using a double-sided tape.
Examples of the solid hot melt adhesive include styrene-butadiene rubber (SBR) adhesives and olefin adhesives (adhesives such as polyethylene, polypropylene and poly1-butene).
Examples of the solution-based adhesive include an acrylic resin-based adhesive and an ethylene-vinyl acetate-based adhesive.
Further, as the adhesive, an adhesive having flame retardancy is preferable. If a flame-retardant adhesive is used, the flame-retardant property of the flame-retardant sound absorbing material is further improved.

The coating amount of the adhesive (solid content per unit area) is preferably ^{1~20g / m 2, 5~10g / m} 2 is more preferable.
When a solution-based adhesive is used as the adhesive, the coating amount is the dry coating amount.

A laminate in which at least a rubber layer, a middle layer, and a surface layer (I) are laminated in this order can be produced, for example, as follows.
First, in the same manner as in the first embodiment, a surface layer is adhered to one surface of the middle layer to form a laminated body S', and the laminated body S'is passed through a press roll to obtain a desired basis weight, thickness, and appearance. Molding is performed so as to have a density, and a laminated body T'is obtained.
Then, an adhesive is applied to one surface of the sheet-shaped rubber layer to form an adhesive layer. The laminate T'is laminated on the adhesive layer so that the middle layer of the laminate T'and the adhesive layer are adjacent to each other.
Then, the rubber layer, the middle layer, and the surface layer (I) are laminated in this order by performing a press punching process using a punching die according to the use of the flame-retardant sound absorbing material. As the rubber layer, a flame-retardant sound absorbing material having a layer structure arranged adjacently on the main surface of the middle layer via an adhesive layer can be obtained.
An adhesive may be applied to the surface of the laminated body T'on the side opposite to the surface layer to form an adhesive layer, and a rubber layer may be laminated on the adhesive layer.
Examples of the adhesive for adhering the middle layer and the rubber layer include those exemplified above as the adhesive for adhering the surface layer (II) and the rubber layer.

As described above, the flame retardant sound absorbing material of the second embodiment of the present invention has, as each surface layer, a porous sheet having a flame retardancy of HF-1 or higher due to UL94, while as a middle layer. It is formed by using flame retardant particles, a raw material fiber (a) containing 40% by mass or more of a fiber (α) having at least one of a hollow tubular shape and a crimped shape, and a heat-sealing fiber (b). It has an air-laid non-woven fabric. Therefore, the flame-retardant sound-absorbing material of the second embodiment of the present invention is excellent in sound absorption and flame retardancy.
Further, since such a middle layer contains particulate flame retardant particles as a flame retardant, there is a concern that the flame retardant particles may fall off, but the flame retardant sound absorbing material of the second embodiment of the present invention has a flame retardant sound absorbing material. Since it has the surface layer (I), it is possible to prevent the flame retardant particles contained in the middle layer from falling to the outside.
Further, since the surface layer (I) contains 10% by mass or less of the flame retardant particles, powder dropping of the flame retardant particles from the surface layer (I) is also suppressed. On the other hand, if the content of the flame retardant particles in the surface layer (II) is 10% by mass or less, the adhesiveness of the rubber layer is enhanced. In addition, it is possible to suppress the powder falling of the flame retardant particles from the surface layer (II) before the rubber layer is adhered (during processing). Further, since each surface layer is formed of a sheet having a flame retardancy of HF-1 or higher due to UL94, the flame retardancy of the flame-retardant sound absorbing material as a whole can also be achieved to be HF-1 or higher. Further, since the sheet forming the surface layer (I) is a porous sheet, it can be effectively attenuated in the middle layer without reflecting noise and vibration from home appliances and the like.
Moreover, since the flame-retardant sound absorbing material of the second embodiment of the present invention has a rubber layer on the other surface of the middle layer, the middle layer cannot completely absorb the noise and vibration, and a part of the noise and vibration is generated. Even if it passes through the middle layer, noise and vibration are reflected by the rubber layer, so it is also excellent in sound insulation. The reflected noise and vibration return to the middle layer and are attenuated in the middle layer.

The flame-retardant sound absorbing material of the second embodiment of the present invention is usually incorporated in a home electric appliance and used in a form of being wound or attached to a motor, a compressor, or the like. Not limited to.

Further, in the flame-retardant sound absorbing material of the second embodiment of the present invention, the surface layer (II) between the middle layer and the rubber layer may or may not be present, but the middle layer and the rubber layer may be present. If there is a surface layer (II) between the two (for example, the form of (1) above), the adhesiveness of the rubber layer is enhanced. When there is no surface layer (II) between the middle layer and the rubber layer (for example, the form of (2) above), the adhesiveness of the rubber layer may be insufficient. In such a case, as described above, it is preferable to laminate the middle layer and the rubber layer via another layer such as an adhesive layer or a tissue layer.
Further, as the surface layer (II), a porous sheet having a flame retardant particle content of more than 10% by mass may be used instead of the porous sheet having a flame retardant particle content of 10% by mass or less. However, considering the adhesiveness of the rubber layer and the powder removal of the flame retardant particles from the surface layer (II) during processing, the content of the flame retardant particles in the surface layer (II) is preferably 10% by mass or less.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
In the following examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

<Porous sheet for surface layer>
[Porous Sheet A]
A pulp sheet made of coniferous bleached kraft pulp (NBKP) was defibrated with a dry defibrator using an air-laid non-woven fabric machine manufactured by Honshu Paper Co., Ltd. to obtain pulp fibers having a length-weighted average fiber length of 2.0 mm. The pulp fibers were dropped and deposited together with an air stream to form a web having ^{a basis weight of 35 g / m 2.}
On the web, 50 parts of EVA emulsion (trade name: Sumikaflex 752, manufactured by Sumitomo Chemtex, 50% non-volatile content dispersion) as a binder is added to 50 parts of a flame retardant guanidine phosphate-based flame retardant (trade name: Apinone-307). , Sanwa Chemical Co., Ltd., an aqueous solution with a concentration of 50%) ^{was sprayed and sprayed so that the solid content was 10.0 g / m 2,} and then hot air (atmosphere temperature 170 ° C.) was passed through. , Pulp fibers were bonded to each other.
Then, the front and back sides of the web are inverted, and the above-mentioned treatment liquid is spray-sprayed on the opposite surface of the surface on which the treatment liquid is spray-sprayed so that the solid content is 10.0 g / m ^2. Again, hot air (atmospheric temperature 170 ° C.) was passed through to obtain a flame-retardant dry air-laid non-woven fabric having ^{a basis weight of 55 g / m 2, which was used as a porous sheet A.}
As a result of the flame retardancy evaluation described later, the porous sheet A was horizontal flame retardant HF-1.
Further, according to JIS-L1096: 1998, the Frazier air permeability was 500 cm ³ / cm ² · s ^-1 .

[Porous sheet B]
Using a guanidine phosphate flame retardant solution (trade name: Apinone-307, solid content concentration 50%, manufactured by Sanwa Chemical Co., Ltd.), PBT melt blown so that ^{the solid content of the guanidine phosphate flame retardant is 7 g / m 2.} Non-woven fabric (trade name: Craflex, basis weight 25 g / m ² , thickness 0.06 mm, made by Kuraray) is impregnated and applied, dried in hot air, and flame retardant ^{with a basis weight of 32.0 g / m 2.} A dry non-woven fabric was obtained, and this was used as a porous sheet B.
As a result of the flame retardancy evaluation described later, the porous sheet B was horizontal flame retardant HF-1. Further, according to JIS-L1096: 1998, the Frazier air permeability was 20 cm ³ / cm ² · s ^-1 .

[Porous Sheet C]
A glass cloth (trade name: glass cloth, basis weight 45 g / m ² , manufactured by Unitika Ltd.) was used as a porous sheet C.
As a result of the flame retardancy evaluation described later, the porous sheet C was horizontal flame retardant HF-1.
Further, according to JIS-L1096: 1998, the Frazier air permeability was 200 cm ³ / cm ² · s ^-1 .

[Porous sheet D]
94 parts of pulp fiber having the same length as that used for producing the porous sheet A and having a weighted average fiber length of 2.0 mm, and phosphorus / nitrogen-based condensate particles (trade name: Nonnen R028-1, average particle diameter 40 μm, round). 6 parts (manufactured by Ryoyu Kagaku Kogyo) were mixed and dropped and deposited together with the air flow to form a web having ^{a basis weight of 75.0 g / m 2.}
A treatment in which 60 parts of the same EVA emulsion used for producing the porous sheet A was added with 40 parts of an aqueous solution of the same guanidine phosphate flame retardant used for producing the porous sheet A on the web. The liquid was spray-sprayed so that the solid content was 8.0 g / m ^2, and then hot air (atmosphere temperature 170 ° C.) was passed to bond the pulp fibers to each other.
Then, the front and back sides of the web are inverted, and the above-mentioned treatment liquid is spray-sprayed on the opposite surface of the surface on which the treatment liquid is spray-sprayed so that the solid content is 8.0 g / m ^2. Again, hot air (atmospheric temperature 170 ° C.) was passed through to obtain a flame-retardant dry air-laid non-woven fabric having ^{a basis weight of 91.0 g / m 2, which was used as a porous sheet D.}
As a result of the flame retardancy evaluation described later, the porous sheet D was horizontal flame retardant HF-1.
Further, according to JIS-L1096: 1998, the Frazier air permeability was 400 cm ³ / cm ² · s ^-1 .

[Porous sheet E]
80 parts of pulp fiber with the same length-weighted average fiber length of 2.0 mm as used in the production of the porous sheet A, and 20 parts of the same phosphorus-nitrogen condensate particles as those used in the production of the porous sheet D. And were mixed and dropped and deposited together with the air flow to form a web having ^{a basis weight of 70 g / m 2.}
A treatment in which 80 parts of the same EVA emulsion used for producing the porous sheet A was added with 20 parts of an aqueous solution of the same guanidine phosphate flame retardant used for producing the porous sheet A on the web. The liquid was spray-sprayed so that the solid content was 10.0 g / m ^2, and then hot air (atmosphere temperature 170 ° C.) was passed to bond the pulp fibers to each other.
Then, the front and back sides of the fiber sheet were inverted, and the above-mentioned treatment liquid was spray-sprayed on the opposite surface of the surface on which the treatment liquid was spray-sprayed so that the solid content was 10.0 g / m ² . After that, hot air (atmospheric temperature 170 ° C.) was passed through again to obtain a flame-retardant dry air-laid non-woven fabric having ^{a basis weight of 90.0 g / m 2, which was used as a porous sheet E.}
As a result of the flame retardancy evaluation described later, the porous sheet E was horizontal flame retardant HF-1.
Further, according to JIS-L1096: 1998, the Frazier air permeability was 500 cm ³ / cm ² · s ^-1 .

[Porous sheet F]
The PBT melt blown non-woven fabric used for producing the porous sheet B was designated as the porous sheet F.
As a result of the flame retardancy evaluation described later, the porous sheet F failed the horizontal flame retardancy.

[Porous sheet G]
Pulp fibers having the same length as that used for producing the porous sheet A and having a weighted average fiber length of 2.0 mm were dropped and deposited together with an air flow to form a web.
The same EVA emulsion used for producing the porous sheet A ^{was spray-sprayed on the web so that the solid content was 4.5 g / m 2,} and then hot air (atmospheric temperature 170 ° C.) was passed through the web. The pulp fibers were bonded to each other.
Then, the front and back sides of the fiber sheet are inverted, and the EVA emulsion is spray-sprayed again on the opposite surface of the surface on which the EVA emulsion is spray-sprayed so that the solid content is 4.5 g / m ^2. , Hot air (atmospheric temperature 170 ° C.) was passed through to obtain a dry air-laid non-woven fabric having ^{a basis weight of 45 g / m 2, which was used as a porous sheet G.}
As a result of the flame retardancy evaluation described later, the porous sheet G failed the horizontal flame retardancy.

[Example 1]
A flame-retardant sound-absorbing sheet including a surface layer (I) made of a porous sheet A, a surface layer (II) made of a porous sheet A, and a middle layer using pulp fiber as a raw material fiber is manufactured as follows. did.
The porous sheet A (surface layer (I)) was fed out on a mesh conveyor having a suction box, and 5 g / m ² of PET powder (powder adhesive) was sprayed on the porous sheet A with a spray device. .. Next, fluff pulp (product number: NB-416, manufactured by Weyerhaeuser) and heat-sealing fiber (PET / PET composite synthetic fiber (trade name: Casben # 7080, manufactured by Unitika, fineness 2.2 dtex, length weighted). Average fiber length 5 mm)) and phosphorus-nitrogen condensate particles (trade name: Nonnen R028-1, manufactured by Maruhishi Yuka Kogyo, average particle diameter 40 μm), which are flame retardant particles, are mixed and solved in air. An air-laid web (middle layer) was formed on the porous sheet A using a fiber-dried air-laid web forming device.
The fluff pulp, the heat-fusing fiber and the flame retardant particles are mixed, defibrated, and defibrated so that the mass ratio is fluff pulp: heat-fusing fiber: flame retardant particle = 60: 20: 20. It was used so that the basis weight of the air-laid web formed was 490 g / m ^2.
Then, the same PET powder (powder adhesive) used earlier is sprayed on the air-laid web by a layered spraying device, and a porous sheet A (surface layer (II)) is further applied thereto. It was fed out in a laminated manner and led to a hot air dryer, and heated above the melting point of the sheath so that the sheath of the heat-sealing fiber melted.
As a result, the porous sheet A was adhered to both sides of the air-laid web containing the flame retardant particles to form the laminated body S.
Then, the laminate S was further passed through a press roll and molded so as to have the basis weight, thickness, and apparent density shown in Table 1 to obtain the flame-retardant sound absorbing material of Example 1.

With respect to the obtained flame retardant sound absorbing material, the Frazier air permeability was measured by the method described later, and the flame retardancy, the powder falling of the flame retardant particles, and the sound absorption coefficient (sound absorbing property) were measured and evaluated. The results are shown in Table 1. Table 1 shows the basis weight and thickness of each layer and the obtained flame-retardant sound absorbing material.
The basis weight and thickness of the surface layers (I) and (II) are actually measured values. The basis weight of the middle layer is a value obtained by actually measuring the basis weight of the flame-retardant sound absorbing material and subtracting the basis weight of the surface layers (I) and (II) from the measured value. The thickness of the middle layer is a value obtained by actually measuring the thickness of the flame-retardant sound absorbing material and subtracting the thicknesses of the surface layers (I) and (II) from the measured value. The apparent density of the flame-retardant sound absorbing material was calculated from the basis weight and thickness. An upright dial gauge was used to actually measure the thickness (meter diameter: 30 mm, measured load pressure: 20 g / cm ² ).

[Evaluation method]
(Frazier air permeability)
It was measured according to JIS-L1096: 1998.
In Example 10, the laminated body (laminated body T described later) before laminating the rubber layer on the porous sheet A (surface layer (II)) was measured.

(Flame retardant (horizontal flame retardant test))
The test was carried out according to the horizontal flame retardant test HF (ISO3582, JIS K6400, ASTM D4986) of the foam material of UL94 (Under Laboratories, USA), and it was tested whether or not it passed HF-1. If it passed, it was described as "HF-1" in the table.
Specifically, the flame-retardant sound absorbing material obtained in Example 1 was cut into a size of 150 ± 1 (mm) × 50 ± 1 (mm), and this was used as a test piece. The test piece was held horizontally, a 38 mm flame was indirectly flamed for 60 seconds, and a judgment was made based on the combustion speed and combustion behavior of 100 mm between marked lines.
The test was performed on 5 test pieces.
(1) The burning time of at least 4 of the 5 test pieces is 2 seconds or less (1 piece may exceed 2 seconds but 10 seconds or less);
(2) Burning + glowing time of each test piece must be within 30 seconds;
(3) The damaged length of each test piece is 60 mm or less;
(4) No cotton ignition due to dripping material;
If all of the above are satisfied, HF-1 is passed.

(Powder drop)
The flame-retardant sound absorbing material obtained in Example 1 was tapped 10 times on black paper so that its end surface (the surface perpendicular to the surface direction of the sheet) was facing downward, and the powder that fell off on the black paper ( Flame retardant particles) were fixed with transparent adhesive tape. The amount of powder on the black paper was visually evaluated in the following two stages.
◯: There is little powder on the black paper, and the adhesiveness of the transparent adhesive tape on which the powder is fixed remains.
X: There is a lot of powder on the black paper, and the adhesiveness of the fixed transparent adhesive tape is lost.

(Sound absorption coefficient and sound absorption)
The vertical incident sound absorption coefficient measurement at 3150 Hz was performed according to JIS A1405-2: 2007.
Since the sound absorption coefficient of the material changes depending on the angle at which the sound is incident, the value of the sound absorption coefficient differs depending on the measurement method. The sound absorption coefficient measured under the condition that sound is vertically incident on the material using an acoustic tube is called "vertical incident sound absorption coefficient". "Vertical incident sound absorption coefficient" is used for developing sound absorbing materials and grasping their characteristics.
Specifically, first, the sample is attached to the end of the acoustic tube (the air layer behind the sample is 0 mm). The size of the sample is φ29 mm for treble (for 500 to 6400 Hz). Then, noise sound is radiated from the speaker in the acoustic tube to generate a sound field in the acoustic tube. Then, the sound pressure signals of the two microphones are FFT analyzed to _{calculate the complex sound pressure transfer function H 12} between the microphones, and the "vertical incident sound absorption coefficient" at 3150 Hz is calculated from the function.
The sound absorption property was evaluated in the following three stages according to the calculated sound absorption coefficient.
⊚: Sound absorption coefficient is 70% or more ○: Sound absorption coefficient is less than 70% 40% or more ×: Sound absorption coefficient is less than 40%

[Examples 2 to 9]
A flame-retardant sound absorbing sheet was produced in the same manner as in Example 1 except that the configurations of the surface layer (I), the middle layer, and the surface layer (II) were changed as shown in Table 1, respectively, and the same as in Example 1. Items were measured and evaluated. The results are shown in Table 1.
In Examples 2 to 5, and Examples 8 and 9, the same fluff pulp as that used in Example 1 was used as the raw material fiber used for producing the middle layer.
In Example 6, as the hollow tubular raw material fiber used for producing the middle layer, a polylactic acid hollow fiber (trade name: PLA fiber "HP8F", fineness: 17dtex, length-weighted average fiber length: 5 mm, manufactured by Unitika Ltd. ) Was used.
In Example 7, as the raw material fiber used for producing the middle layer, polyester latent crimp fiber (trade name: latent crimp fiber "C81", fineness: 2.2 dtex, length-weighted average fiber length: 5 mm, Unitika Ltd. Made) was used. The latent crimp fibers are crimped by heat treatment with a hot air dryer when forming the middle layer.

[Comparative Examples 1, Comparative Examples 3 to 5]
A three-layered sheet was produced in the same manner as in Example 1 except that the configurations of the surface layer (I), the middle layer, and the surface layer (II) were changed as shown in Table 2, respectively, and the same as in Example 1. Items were measured and evaluated. The results are shown in Table 2.
In Comparative Example 1, as the raw material fiber used for producing the middle layer, rayon chop (trade name: rayon chop fiber "Corona", fineness: 1.7 dtex, length weighted) which does not correspond to either hollow tubular or crimped shape. Average fiber length: 5 mm, manufactured by Daiwa Bow Rayon Co., Ltd.) was used.

[Comparative Example 2]
A sheet without the surface layer (I) and the surface layer (II) and consisting only of the middle layer was produced as follows.
A breathable carrier sheet is fed out on a mesh conveyor having a suction box, and fluff pulp, heat-sealing fibers and flame retardant particles are mixed and defibrated in air in the same manner as in Example 1, and then dried. The air-laid web (middle layer) was formed on the carrier sheet using the air-laid web forming device of the above. Then, after another carrier sheet was layered on this, it was guided to a hot air dryer and heated above the melting point of the sheath so that the sheath of the heat-sealing fiber was melted.
Then, it was passed through a press roll and molded so as to have the basis weight, thickness, and apparent density shown in Table 2, and then the carrier sheets on both sides were peeled off to obtain the sheet of Comparative Example 2.
The obtained sheet was measured and evaluated for the same items as in Example 1.
The results are shown in Table 2.

[Comparative Example 6]
A stack of 10 porous sheets A is used as a sheet of Comparative Example 6 (thickness 6.0 mm, basis weight 550.0 g / m ² , apparent density 0.092 g / cm ³ , Frazier air permeability 80 cm ³ / cm ² · s). ^-1 ).
When the same items as in Example 1 were measured and evaluated for the obtained sheet, the flame retardancy passed HF-1 and the powder drop was "○", but the sound absorption coefficient was high. It was low and the sound absorption was "x".

The flame-retardant sound-absorbing material of each example was excellent in sound-absorbing property and flame-retardant property, and powder falling of the contained flame retardant agent particles was also suppressed.
On the other hand, the sheet of Comparative Example 1 was a rayon chop in which the raw material fiber in the middle layer did not correspond to either a hollow tubular shape or a crimped shape, and was inferior in sound absorption. Since the sheet of Comparative Example 2 has a one-layer structure and does not have a surface layer, and in the sheet of Comparative Example 3, the surface layer (I) contains flame retardant particles in an amount of 10% by mass or more in the surface layer (I). Therefore, the powder was noticeably dropped in each case.
In each of the sheets of Comparative Examples 4 and 5, the flame retardancy of the surface layer (I) was insufficient, so that the flame retardancy of the sheet as a whole was inferior. The sheet of Comparative Example 6 in which only the flame-retardant sheet of HF-1 was superposed had sufficient flame retardancy but was inferior in sound absorption.

[Example 10]
A flame-retardant sound-absorbing sheet having a surface layer (I) made of a porous sheet A, a surface layer (II) made of a porous sheet A, a middle layer using pulp fibers as raw material fibers, and a rubber layer is described below. Manufactured as.
First, in the same manner as in Example 1, a porous sheet A is adhered to both sides of an air-laid web containing flame retardant particles to form a laminate S, and the obtained laminate S is further passed through a press roll. The laminate T was obtained by heat molding. The heating temperature when passing through the press roll was 130 ° C.
Next, an SBR hot melt adhesive was applied on the main surface of a ^{rubber layer (thickness 2 mm, density 1.8 g / cm 3} ) composed of EPDM, IIR, barium sulfate and calcium carbonate, and the amount applied was 5 g / m. ^{An adhesive layer was formed by extruding coating (film formation) so as to be No. 2,} and the laminated body T was laminated on the adhesive layer to obtain a laminated body U. The adhesive layer and the laminated body T were laminated so that the main surface of the adhesive layer and the main surface of the surface layer (II) made of the porous sheet A were adjacent to each other.
As a result, the porous sheet A was adhered to both sides of the air-laid web containing the flame retardant particles, and the rubber layer was further adhered to the surface of one of the porous sheets A to form the laminated body U.
Then, the laminated body U was press-pulled using an arbitrary die to obtain the flame-retardant sound absorbing material of Example 10.

With respect to the obtained flame retardant sound absorbing material, the Frazier air permeability was measured in the same manner as in Example 1, and the flame retardancy, the powder falling of the flame retardant particles, and the sound absorption coefficient (sound absorbing property) were measured and evaluated. The results are shown in Table 3.
Table 3 shows the basis weight, thickness, and apparent density of the obtained flame-retardant sound absorbing material.
In addition, the sound insulation was evaluated by the method described later. The results are shown in Table 3.

[Measuring method]
(Sound insulation)
For the evaluation of sound insulation, the sound absorption coefficient / transmission loss measurement method using a vertical incident acoustic measurement (acoustic tube) system was adopted. As a measuring instrument, a "vertical incident sound absorption coefficient / transmission loss measurement system (9301 type)" manufactured by Rion Co., Ltd. was used.
A flame-retardant sound absorbing material was set in a predetermined place on the measuring instrument. The sound emitted from the speaker installed at the end inside the acoustic tube and incident on the flame-retardant sound absorbing material (incident sound) is measured by two microphones installed on the front side (speaker side) of the flame-retardant sound absorbing material. did. Further, the sound (transmitted sound) after passing through the flame-retardant sound absorbing material was measured by two microphones installed behind the flame-retardant sound absorbing material. The incident sound and the transmitted sound were measured according to JIS A 1405-2 (ISO 10534-2: 1998).
Next, the curve of the measurement data is approximately expressed using dedicated software (vertical incident / transmission loss characteristic estimation software, manufactured by Rion Co., Ltd.), and the mass law curve of transmission loss is estimated and calculated with a large material size. Sound insulation was evaluated in two stages.
◯: The minimum value when the 1/3 oct frequency is between 500 and 6000 Hz is 30 dB or less ×: The minimum value when the 1/3 oct frequency is between 500 and 6000 Hz is over 30 dB.

The flame-retardant sound-absorbing material of Example 10 was excellent in sound-insulating property in addition to sound-absorbing property and flame-retardant property, and powder falling of the contained flame retardant agent particles was suppressed.

Claims (9)

A flame-retardant sound absorbing material composed of a middle layer and a surface layer provided on at least one surface of the middle layer.
The surface layer is made of a porous sheet having a flame retardant particle content of 10% by mass or less and a flame retardant property of UL94 of HF-1 or more.
The middle layer contains flame retardant particles having an average particle diameter of 10 to 500 μm, raw material fibers (a) containing 40% by mass or more of fibers (α) having at least one of hollow tubular and crimped forms, and heat. A flame-retardant sound absorbing material, which is made of an air-laid non-woven fabric formed by using a fusible fiber (b). The flame-retardant sound absorbing material according to claim ¹ , wherein the Frazier air permeability according to JIS-L1096: 1998 is 5 to 100 ^{cm 3} / cm ² · s -1. A flame-retardant sound absorbing material comprising a middle layer, a surface layer provided on one surface of the middle layer, and a rubber layer provided on the other surface of the middle layer.
The surface layer is made of a porous sheet having a flame retardant particle content of 10% by mass or less and a flame retardant property of UL94 of HF-1 or more.
The middle layer contains flame retardant particles having an average particle diameter of 10 to 500 μm, raw material fibers (a) containing 40% by mass or more of fibers (α) having at least one of hollow tubular and crimped forms, and heat. A flame-retardant sound absorbing material, which is made of an air-laid non-woven fabric formed by using a fusible fiber (b). The flame-retardant sound absorbing material according to claim 3, further comprising a surface layer between the middle layer and the rubber layer. The flame-retardant sound absorbing material according to claim 3 or 4, wherein the part excluding the rubber layer has a Frazier air permeability according to JIS-L1096: 1998 of 5 to 100 ^{cm 3} / cm ² · s ^-1. The flame-retardant sound absorbing material according to any one of claims 1 to 5, wherein the fiber (α) contains pulp fiber. The flame-retardant sound-absorbing material according to any one of claims 1 to 6, wherein the ratio of the thickness of the middle layer to the thickness of the flame-retardant sound-absorbing material is 70 to 99.8%. The flame-retardant sound absorbing material according to any one of claims 1 to 7, wherein the content of the raw material fiber (a) in the middle layer is 20 to 70% by mass. The basis weight of the surface layer is 20 to 60 g / m. ² The flame-retardant sound absorbing material according to any one of claims 1 to 8.