Patent Description:
In recent years, quietness has been more emphasized than ever as one of commercial values of products in automobiles and electric products. In general, it is thought to be effective to increase the mass and thickness of a sound-absorbing material that serves as a countermeasure component in noise control. However, from the viewpoint of keeping a large space inside automobiles and living rooms as well as reducing fuel consumption in automobiles, weight reduction and compactification of sound-absorbing materials have been required. In addition, in automobiles, a technique of shaping a sound-absorbing material into a shape of a part by molding processing is frequently used in order to make the sound-absorbing material follow a complicated shape such as a body of an automobile and install the sound-absorbing material compactly.

Patent Document <NUM> proposes a molded article for a sound-absorbing material in which a composite material containing a base material made of a non-woven fabric or a resin foam and a skin material is clamped with a mold.

Further, Patent Document <NUM> proposes a sound-absorbing material including a fiber assembly containing a high-softening-point synthetic fiber staple having a fineness of <NUM> to <NUM> denier, a medium-softening-point synthetic fiber staple having a fineness of <NUM> to <NUM> denier, and a low-softening-point synthetic fiber staple having a fineness of <NUM> to <NUM> denier. Here, the thickness of a thread that is <NUM> long and weighs <NUM> is defined as "<NUM> denier"; which means that <NUM> tex = denier × <NUM>.

Patent Document <NUM> discloses a non-woven-fabric layered body for a sound-absorbing material, in which a non-woven fabric layer α and a non-woven fabric layer ß are layered, wherein the non-woven fabric layer α contains first type short fibers (<NUM>% by weight of a <NUM> denier black polyester (PET) fiber; <NUM> denier = <NUM> dtex), second type short fibers (<NUM> by weight of a <NUM> denier black PET fiber; <NUM> denier = <NUM> dtex), and third type short fibers containing a resin in an outer surface layer (<NUM>% by weight of a <NUM> denier (<NUM> decitex) low melt binder fiber; the fiber is a core-sheath polyester fiber with a lower melting temperature sheath), wherein a total content mass of the first type short fibers and the second type short fibers with respect to a total mass of the non-woven fabric layer α is <NUM>% by mass (<NUM> % + <NUM> %, respectively), and a content mass of the third type of short fibers Cl with respect to the total mass of the non-woven fabric layer α is <NUM>% by mass; wherein the non-woven fabric layer β contains short fibers containing a polyester resin, the content mass of these short fibers with respect to a total mass of the non-woven fabric layer β being <NUM> by mass; wherein the non-woven fabric layer α and the non-woven fabric layer β are heat-set at <NUM> to melt the low-melt fibers and bond the nonwoven layers α and β.

Patent Document <NUM> discloses a sound absorbing liner comprising at leat one fibrous layer conistring f fuibers and a thermoset binder thermally molded to form the liner, wherein the fibers comprise thermoplastic side-by-side fibers whose sides differ such that the fiber has a frizzy or curved shape. The staple fiber length of frizzy fibers is between <NUM> and <NUM>; the fiber is preferably <NUM> to <NUM> dtex, more preferably <NUM> to <NUM> dtex.

Patent Document <NUM> and Patent Document <NUM> disclose resin fibres where at least a sheath has a melting point that falls in the range of <NUM> and <NUM>, respectively.

According to findings by the present inventors, since the molded article for a sound-absorbing material disclosed in Patent Document <NUM> is molded by heating a non-woven fabric containing a yarn having a low melting point, it is easy to impart a shape by molding processing. However, in a case where the low-melting-point yarn having a low melting point is used or a large content mass thereof is used, there is a problem that the thickness after molding processing is reduced due to the adhesion action when the low-melting-point yarn is melted and re-solidified, and as a result, the sound-absorbing performance becomes poor.

On the other hand, since the sound-absorbing material disclosed in Patent Document <NUM> contains a high-softening-point synthetic fiber staple having a relatively high softening point, the heat resistance assuming a temperature rise inside automobiles tends to be relatively excellent. However, in a case where the content of the medium-softening-point synthetic fiber staple is large, there is a problem that the thickness after molding processing is reduced due to the melting and the adhesion action, and as a result, the sound-absorbing performance becomes poor.

Furthermore, there is a problem that the surface of the sound-absorbing material is likely to be scraped or break due to friction between the sound-absorbing material such as a non-woven fabric and the mold during molding processing. Therefore, in view of the above circumstances, an object of the present invention is to provide a non-woven-fabric layered body for a sound-absorbing material which has a good sinking repulsive force during molding, is excellent in thickness recoverability, is excellent in molding followability to a body or the like of an automobile having a complicated shape, and is excellent in sound-absorbing performance.

According to the present invention, it is possible to provide a non-woven fabric for a sound-absorbing material which is excellent in thickness recoverability during molding, is excellent in followability to a body or the like of an automobile having a complicated shape, and is excellent in sound-absorbing performance. Furthermore, it is possible to obtain a sound-absorbing material having a non-woven fabric for a sound-absorbing material as a base material and having a non-woven fabric layer for a skin.

In a non-woven-fabric layered body for a sound-absorbing material of the present invention, a non-woven fabric layer α and a non-woven fabric layer β are layered. The non-woven fabric layer α contains short fibers A having a fineness of <NUM> to <NUM> dtex and short fibers B having a fineness of <NUM> to <NUM> dtex, the total content mass of the short fibers A and the short fibers B with respect to the total mass of the non-woven fabric layer α is <NUM> to <NUM>% by mass, and the content mass ratio of the short fibers A and the short fibers B (content mass of short fibers A/content mass of short fibers B) is <NUM> to <NUM>. The non-woven fabric layer α further contains short fibers C1 containing a resin having a melting point of <NUM> to <NUM> in the outer surface layer, and the content mass of the short fibers C1 with respect to the total mass of the non-woven fabric layer α is <NUM> to <NUM>% by mass. The non-woven fabric layer β contains short fibers C2 containing a resin having a melting point of <NUM> to <NUM> in the surface layer, and the content mass of the short fibers C2 with respect to the total mass of the non-woven fabric layer β is <NUM> to <NUM>% by mass.

In the non-woven fabric layer α, the short fibers A, the short fibers B, and the short fibers C1 are uniformly mixed in a portion that becomes a part of the base material of the sound-absorbing material. Due to the short fibers A being contained, a large number of fine pores are formed, and excellent sound-absorbing performance can be obtained. Further, the short fibers B having a higher fineness than that of the short fibers A form a large number of fine pores, have high rigidity, and contribute to the thickness recoverability during molding processing. By adjusting the content mass ratio of the short fibers A and the short fibers B and uniformly mixing them, the sound-absorbing performance and the thickness recoverability during molding processing are improved.

That is, such a non-woven-fabric layered body for a sound-absorbing material (hereinafter this may be simply referred to as a "non-woven fabric") has the non-woven fabric layer α having the above configuration, and thus has excellent thickness recoverability during molding in heating and compression during molding. In addition, the sound-absorbing material can secure a thickness for exhibiting sound-absorbing performance, and the sound-absorbing performance is excellent due to air friction of the fine porous portion inside the non-woven fabric layer α.

Furthermore, by having the non-woven fabric layer β having the above configuration, it is possible to curb breakage of the non-woven fabric layer due to friction between the non-woven-fabric layered body for a sound-absorbing material and the mold in heating and compression during molding, excellent followability to the mold is obtained, and thus it is possible to mold the non-woven fabric layer into a required shape. In addition, the non-woven fabric layer β may be at least on one surface side of the non-woven fabric layer α, but may be on both surface sides. Since the sound-absorbing material is provided with a skin material, which will be described later, on the other surface side of the non-woven fabric layer α in the molding processing, by having the non-woven fabric layer β on one surface side that comes into contact with the mold, breakage of the non-woven fabric layer can be curbed, excellent followability to the mold is obtained, and thus it is possible to mold the non-woven fabric layer into a required shape.

Here, when the content of the short fibers C1 in the non-woven fabric layer α is increased, the content of the resin contained in the short fibers C1 in the non-woven fabric layer α is increased, and the thickness during molding processing is reduced due to the adhesion action when the resin at <NUM> to <NUM> is melted and re-solidified, it is thus difficult to obtain thickness recoverability. Therefore, in the present invention, by minimizing the content of the short fibers C1 in the non-woven fabric layer α and increasing the content of the short fibers C2 in the non-woven fabric layer β, a non-woven fabric for a sound-absorbing material having good thickness recoverability during molding processing and excellent sound-absorbing performance can be obtained.

Then, the non-woven fabric layer α and the non-woven fabric layer β are layered, and the interface is partially fused to obtain a non-woven-fabric layered body. The "partial fusion" of the non-woven fabric layer α and the non-woven fabric layer β melts a resin contained in the outer surface layer of the short fibers C2 contained in the non-woven fabric layer β to bind some of the short fibers A, the short fibers B, or the short fibers C1 of the non-woven fabric layer α and some of the short fibers C2 and other short fibers of the non-woven fabric layer β. That is, the resin is obtained by bonding fibers to each other centering on a part where single fibers intersect, and the layered surface is in a partially adhering state rather than entirely adhering.

For the interface between the non-woven fabric layer α and the non-woven fabric layer β, it is important that the layered state of the non-woven fabric layer α and the non-woven fabric layer β do not change during molding processing. When the layered state changes, there is a concern that respective non-woven fabric layers may peel off or a stack may occur during molding processing, and accordingly, it become difficult to maintain sound-absorbing performance. For this reason, in the non-woven fabric layer β, in addition to curbing breakage of the non-woven fabric for a sound-absorbing material due to friction between the non-woven fabric for a sound-absorbing material and the mold in heating and compression during the molding, it is also necessary to maintain the layered state. The short fibers C2 contained in the non-woven fabric layer β bond some of the short fibers of the non-woven fabric layer α and the non-woven fabric layer β to be layered. Therefore, the melting point of the resin contained in the outer surface layer of the short fibers C2 contained in the non-woven fabric layer β is preferably lower than the melting point of the resin contained in the outer surface layer of the short fibers C1.

The non-woven fabric layer α contains short fibers A having a fineness of <NUM> to <NUM> dtex and short fibers B having a fineness of <NUM> to <NUM> dtex. Due to containing the short fibers A having a fineness of <NUM> to <NUM> dtex being contained, a porous portion having a large number of fine pores can be formed inside the non-woven fabric for a sound-absorbing material, and the sound-absorbing performance of the sound-absorbing material using this non-woven fabric is excellent.

By setting the fineness of the short fibers A to <NUM> dtex or more, in the carding process when producing the non-woven fabric layer α, yarn breakage and winding around the card clothing are curbed, the short fibers A uniformly disperse in the non-woven fabric layer α, a porous portion having a large number of fine pores can be formed inside the non-woven fabric layer α, and the sound-absorbing performance when used as a sound-absorbing material is excellent. On the other hand, by setting the fineness of the short fibers A to <NUM> dtex or less, a porous portion having a large number of fine pores can be formed inside the non-woven fabric layer α by the short fibers A having a small fineness. As a result, when sound passes through voids between fibers, that is, the porous portion, the sound can be efficiently converted into heat by air friction with fibers around the voids, and excellent sound absorption performance can be obtained when the non-woven fabric is used as a sound-absorbing material. From the above viewpoint, the fineness of the short fibers A is preferably <NUM> to <NUM> dtex, and more preferably <NUM> to <NUM> dtex.

Since the non-woven fabric layer α included in the non-woven-fabric layered body of the present invention contains the short fibers B having a fineness of <NUM> to <NUM> dtex, the rigidity of the short fibers B can impart thickness recoverability during molding to the non-woven fabric of the present invention. By setting the fineness of the short fibers B to <NUM> dtex or more, the rigidity of the short fibers B can impart thickness recoverability during molding to the non-woven fabric of the present invention. On the other hand, by setting the fineness of the short fibers B to <NUM> dtex or less, a porous portion having a large number of fine pores can be formed inside the non-woven fabric layer α, and the sound-absorbing performance when used as a sound-absorbing material is excellent. From the above viewpoint, the fineness of the short fibers B is preferably <NUM> to <NUM> dtex, and particularly preferably <NUM> to <NUM> dtex.

In the non-woven fabric layer α included in the non-woven-fabric layered body of the present invention, the total content mass of the short fibers A and the short fibers B with respect to the total mass of the non-woven fabric layer α is <NUM> to <NUM>% by mass, and the content mass ratio of the short fibers A and the short fibers B (content mass of short fibers A/content mass of short fibers B) is <NUM> to <NUM>. By setting the total content of the short fibers A and the short fibers B and the content mass ratio thereof within the above ranges, it is possible to achieve both the thickness recoverability during molding and the sound-absorbing performance when used as a sound-absorbing material. By setting the total content mass of the short fibers A and the short fibers B to <NUM>% by mass or more, excessive fusion between fibers due to the short fibers C1, which will be described later, can be suppressed, and the thickness recoverability can be maintained even in heating and compression during molding. As a result, a thickness for exhibiting sound-absorbing performance, that is, a porous portion having fine pores is formed inside the non-woven fabric layer α, and sound-absorbing performance is excellent. On the other hand, when the total content mass of the short fibers A and the short fibers B is <NUM>% by mass or less, the form as the non-woven fabric layer α can be maintained, and the non-woven fabric for a sound-absorbing material can be conveyed and handled during molding processing. Furthermore, it is possible to reduce the number of fibers falling off when the sound-absorbing material is cut. From the above point of view, the total content mass of the short fibers A and the short fibers B is preferably <NUM> to <NUM>% by mass, and particularly preferably <NUM> to <NUM>% by mass.

Furthermore, by setting the content mass ratio of the short fibers A and the short fibers B (content mass of the short fibers A/content mass of the short fibers B) to <NUM> to <NUM>, it is possible to achieve both the thickness recoverability during molding and the sound-absorbing performance when used as a sound-absorbing material. Since the non-woven fabric layer α is made of a material in which the short fibers A, the short fibers B, and the short fibers C1 are mixed in advance, the non-woven fabric layer α is not a layer having a layer configuration made of specific short fibers but a non-woven fabric in which each constituent fiber uniformly disperses in the non-woven fabric layer α.

Therefore, the short fiber A forms a fine porous portion inside the non-woven fabric layer α, and plays a role of improving sound-absorbing performance. In addition, the short fibers B play a role of imparting thickness recoverability during molding due to the rigidity thereof. When the content mass ratio of the short fibers A and the short fibers B is <NUM> or more, a fine porous portion can be formed inside the non-woven fabric layer α, and the sound-absorbing performance can be improved. On the other hand, by setting the content mass ratio of the short fibers A and the short fibers B to <NUM> or less, the rigidity of the short fibers B can impart thickness recoverability during molding, and the thickness for exhibiting sound-absorbing performance, that is, a porous portion can be formed. In addition, due to the short fibers B having a relatively high fineness being contained at a constant mass ratio, even in a case where the short fibers A have a small fineness, yarn breakage of the short fibers A and winding of the short fibers A around the card clothing are curbed in the carding process, the short fibers A uniformly disperse, a fine porous portion can be formed inside the non-woven fabric layer α, and the sound-absorbing performance when used as a sound-absorbing material is excellent. From the above viewpoint, the content mass ratio of the short fibers A to the short fibers B is preferably <NUM> to <NUM>, and particularly preferably <NUM> to <NUM>.

The non-woven fabric layer α included in the non-woven-fabric layered body of the present invention contains the short fibers C1 containing a resin having a melting point of <NUM> to <NUM>, and the content mass of the short fibers C1 with respect to the total mass of the non-woven fabric layer α is <NUM> to <NUM>% by mass. By setting the melting point of the resin contained in the short fiber C1 and the content mass of the short fibers C1 within the above ranges, it is possible to achieve all of the thickness recoverability during molding, the conveyance and handling properties of the non-woven fabric for a sound-absorbing material, and further, the number of fibers falling off when the sound-absorbing material is cut being reduced. By setting the melting point of the resin contained in the short fibers C1 to <NUM> or higher, in the stage of producing the non-woven fabric layer α, the fusion of the constituent fibers of the non-woven fabric layer α by the short fibers C1 can be suppressed, and the thickness recoverability can be maintained even in heating and compression during molding. On the other hand, by setting the melting point of the resin contained in the short fibers C1 to <NUM> or lower, in the stage of producing the non-woven fabric layer α, by fusing the constituent fibers of the non-woven fabric layer α with the short fibers C1, it is possible to achieve the conveyance and handling properties of the non-woven fabric for a sound-absorbing material, and further, to reduce the number of fibers falling off when the sound-absorbing material is cut. From the above point of view, the melting point of the resin contained in the short fibers C1 is preferably <NUM> to <NUM>, and particularly preferably <NUM> to <NUM>.

In addition, by setting the content mass of the short fibers C1 with respect to the total mass of the non-woven fabric layer α to <NUM>% by mass or more, in the stage of producing the non-woven fabric layer α, by fusing the constituent fibers of the non-woven fabric layer α with the short fibers C1, it is possible to achieve the conveyance and handling properties of the non-woven fabric for a sound-absorbing material, and further, to reduce the number of fibers falling off when the sound-absorbing material is cut. On the other hand, by setting the content mass of the short fibers C1 with respect to the total mass of the non-woven fabric layer α to <NUM>% by mass or less, the fusion point between the short fibers C1 and the short fibers A and the fusion point between the short fibers C1 and the short fibers B in heating and compression during molding can be reduced, and the thickness recoverability can be maintained even in heating and compression during molding. From the above point of view, the content mass of the short fibers C1 with respect to the total mass of the non-woven fabric layer α is preferably <NUM> to <NUM>% by mass, and particularly preferably <NUM> to <NUM>% by mass.

The non-woven fabric layer α included in the non-woven-fabric layered body of the present invention contains the short fibers C2 containing a resin having a melting point of <NUM> to <NUM> in the outer surface layer, and the content mass of the short fibers C2 with respect to the total mass of the non-woven fabric layer β is <NUM> to <NUM>% by mass. The fibers of the short fibers C2 are not particularly limited, and known fibers can be used, and side-by-side type composite fibers obtained by bonding a low melting point component and a high melting point component, or core-sheath type composite fibers obtained by coating a high melting point component with a low melting point component can be used.

The non-woven fabric layer β contains <NUM> to <NUM>% by mass of other short fibers. As other short fiber materials, thermoplastic resins such as polyester resins, polyamide resins, acrylic resins, and polyolefin resins can be used. Among them, short fibers made of a polyester resin are preferable from the viewpoint of being excellent in heat resistance, that is, being capable of reducing deformation and discoloration of the non-woven fabric for a sound-absorbing material in a high-temperature environment when used in the vicinity of an engine room of an automobile or the like.

By setting the melting point of the resin of the outer surface layer contained in the short fibers C2 and the content mass of the short fibers C2 within the above ranges, the smoothness of the non-woven fabric layer β is improved, breakage of the non-woven fabric for a sound-absorbing material due to friction between the non-woven fabric for a sound-absorbing material and the mold during molding can be curbed, and it is possible to mold the non-woven fabric for a sound-absorbing material into a required shape. Furthermore, in the process of producing the non-woven fabric for a sound-absorbing material, the non-woven fabric layer α and the non-woven fabric layer β can easily adhere to each other, and productivity can be improved. By setting the melting point of the resin contained in the short fibers C2 to <NUM> or higher, in the process of producing the non-woven fabric layer β, adhesion of the resin having a melting point of <NUM> to <NUM> to the production apparatus can be eliminated, and productivity can be improved. On the other hand, by setting the melting point of the resin contained in the short fibers C2 to <NUM> or lower, in the stage of producing the non-woven fabric layer β, by fusing the fibers to each other with the short fibers C2, the smoothness of the non-woven fabric layer β can be improved, and breakage of the non-woven fabric for a sound-absorbing material due to friction between the non-woven fabric for a sound-absorbing material and the mold can be curbed in heating and compression during molding.

It is presumed that the non-woven fabric layer β has a lower basis weight and fewer fluff fibers than the non-woven fabric layer α, and the resin of the outer surface layer of the short fibers C2 melts and closes irregularities of the non-woven fabric surface, and thus the surface becomes smooth. From the above point of view, the melting point of the resin contained in the short fibers C2 is preferably <NUM> to <NUM>, and particularly preferably <NUM> to <NUM>. In addition, by setting the content mass of the short fibers C2 with respect to the total mass of the non-woven fabric layer β to <NUM>% by mass or more, by fusing the fibers to each other with the short fibers C2, the smoothness of the non-woven fabric layer β can be improved, and breakage of the non-woven fabric for a sound-absorbing material due to friction between the non-woven fabric for a sound-absorbing material and the mold can be curbed in heating and compression during molding. Furthermore, in the process of producing the non-woven-fabric layered body for a sound-absorbing material, by fusing the short fibers C2 and the short fibers included in the non-woven fabric layer α, the non-woven fabric layer α and the non-woven fabric layer β can be easily partially fused, and the productivity can be improved. On the other hand, by setting the content mass of the short fibers C2 with respect to the total mass of the non-woven fabric layer β to <NUM>% by mass or less, the tensile elongation at break of the non-woven fabric layer β can be improved, the followability of the non-woven fabric layer β to the mold is improved, and the breakage of the non-woven fabric layer β can be curbed. From the above point of view, the content mass of the short fibers C2 with respect to the total mass of the non-woven fabric layer β is preferably <NUM> to <NUM>% by mass, and particularly preferably <NUM> to <NUM>% by mass. In addition, the smoothness can be measured by a static friction coefficient according to JIS P <NUM>: <NUM><NUM> inclination method.

When the static friction coefficient of the surface on the surface side of the non-woven fabric β of the non-woven-fabric layered body exceeds <NUM>, the friction between the non-woven fabric for a sound-absorbing material and the mold increases in heating and compression during molding, wrinkles and breakage occur on the surface of the non-woven fabric, and sound-absorbing performance and quality are poor, which is not preferable. Therefore, the static friction coefficient is preferably <NUM> or less.

In addition, the short fibers C1 contained in the non-woven fabric layer α included in the non-woven-fabric layered body of the present invention are preferably core-sheath type composite short fibers, and the resin constituting the sheath part is preferably a resin having a melting point of <NUM> to <NUM>. In addition, the sheath part of the core-sheath type composite short fibers corresponds to the outer surface layer. The short fibers C1 are core-sheath type composite fibers, and the fibers contained in the non-woven fabric layer α can adhere to each other by the adhesion action of the resin contained in the sheath part. In addition, by setting the melting point of the resin constituting the sheath part to <NUM> or higher, excessive adhesion between fibers due to the short fibers C1 can be suppressed, and the thickness recoverability can be improved even in heating and compression during molding. On the other hand, by setting the melting point of the resin contained in the sheath part to <NUM> or lower, in the stage of producing the non-woven fabric layer α, by fusing the constituent fibers to each other with the short fibers C1, it is possible to achieve the conveyance and handling properties of the non-woven fabric for a sound-absorbing material, and further, to reduce the number of fibers falling off when the sound-absorbing material is cut. From the above point of view, the melting point of the resin constituting the sheath part is preferably <NUM> to <NUM>, and particularly preferably <NUM> to <NUM>.

In addition, the fineness of the short fibers C1 is preferably <NUM> to <NUM> dtex. When the fineness of the short fibers C1 is <NUM> dtex or more, in the carding process when producing the non-woven fabric layer α, yarn breakage of the short fibers C1 and winding of the short fibers C1 around the card clothing are curbed, the short fibers C1 uniformly disperse, the fibers are fused to each other with the short fibers C1, and accordingly, it is possible to achieve the conveyance and handling properties of the non-woven fabric for a sound-absorbing material, and further, to reduce the number of the fibers falling off when the sound-absorbing material is cut. On the other hand, by setting the fineness of the short fibers C1 to <NUM> dtex or less, the fusion point of the short fibers C1 and the short fibers A or B increases, and it is possible to achieve the conveyance and handling properties of the non-woven fabric for a sound-absorbing material, and further, to reduce the number of fibers falling off when the sound-absorbing material is cut. From the above viewpoint, the fineness of the short fibers C1 is preferably <NUM> to <NUM> dtex, and particularly preferably <NUM> to <NUM> dtex.

In addition, the short fibers C1 are preferably core-sheath type composite short fibers, and in a case where the resin constituting the sheath part is a thermoplastic resin having a melting point of <NUM> to <NUM>, a crystalline resin is preferable. By using the crystalline thermoplastic resin as the resin contained in the short fibers C1, even when the content mass of the short fibers C1 with respect to the total mass of the non-woven fabric layer α is as small as <NUM> to <NUM>% by mass, fusion between the crystalline resin and the short fibers A or B becomes stronger, and it is possible to achieve the conveyance and handling properties of the non-woven fabric for a sound-absorbing material, and further, to reduce the number of fibers falling off when the sound-absorbing material is cut. In addition, since the content mass of the short fibers C1 can be reduced as described above, the fusion point between the short fibers C1 and the short fibers A or B can be reduced in heating and compression during molding, and the thickness recoverability can be maintained even in heating and compression during molding. As such a crystalline resin, a polyester copolymer resin is preferable.

In addition, regarding the crystalline resin in the present invention, a resin having a glass transition point, an exothermic peak (crystallization point) due to crystallization, and an endothermic peak (melting point) due to melting in differential scanning calorimetry is defined as a crystalline resin, and a resin having only at the glass transition point and no endothermic peak (melting point) due to clear melting is defined as an amorphous resin.

Meanwhile, the short fibers C2 are preferably core-sheath type composite short fibers, and the resin constituting the sheath part is preferably a thermoplastic resin having a melting point of <NUM> to <NUM>. In addition, the sheath part of the core-sheath type composite short fibers corresponds to the outer surface layer. The resin constituting the sheath part is preferably a thermoplastic resin having a melting point of <NUM> to <NUM> and an amorphous resin. As such an amorphous resin, a polyester copolymer resin is preferable.

As materials of the short fibers A, the short fibers B, the short fibers C1, and the short fibers C2 of the present invention, thermoplastic resins such as polyester resins, polyamide resins, acrylic resins, and polyolefin resins can be used. Among them, short fibers made of a polyester resin (hereinafter referred to as polyester short fibers) are preferable from the viewpoint of being excellent in heat resistance, that is, being capable of reducing deformation and discoloration of the non-woven fabric for a sound-absorbing material in a high-temperature environment when used in the vicinity of an engine room of an automobile or the like. In addition, the short fibers A and B are preferably short fibers made of a polyethylene terephthalate resin (hereinafter referred to as polyethylene terephthalate short fibers), which are particularly excellent in heat resistance among polyester resins.

The basis weight of the non-woven fabric layer α of the present invention is preferably <NUM>/m<NUM> or more and <NUM>/m<NUM> or less, and the thickness of the non-woven fabric layer α is preferably <NUM> or more and <NUM> or less. By setting the basis weight of the non-woven fabric layer α to <NUM>/m<NUM> or more, the thickness recoverability can be improved even in heating and compression during molding, and many porous portions having fine pores are formed inside the non-woven fabric layer α, and accordingly, excellent sound-absorbing performance is obtained. On the other hand, by setting the basis weight of the non-woven fabric layer α to <NUM>/m<NUM> or less, a non-woven fabric for a sound-absorbing material having excellent lightweight properties can be obtained. From the above viewpoint, the basis weight of the non-woven fabric layer α is preferably <NUM>/m<NUM> or more and <NUM>/m<NUM> or less, and particularly preferably <NUM>/m<NUM> or more and <NUM>/m<NUM> or less. In addition, by setting the thickness of the non-woven fabric layer α to <NUM> or more, the thickness recoverability can be improved even in heating and compression during molding. On the other hand, by setting the thickness of the non-woven fabric layer α to <NUM> or less, it is possible to facilitate transportation of the non-woven fabric for a sound-absorbing material and conveyance efficiency during molding. From the above point of view, the thickness of the non-woven fabric layer α is preferably <NUM> or more and <NUM> or less, and more preferably <NUM> or more and <NUM> or less.

The basis weight of the non-woven fabric layer β is preferably <NUM>/m<NUM> or more and <NUM>/m<NUM> or less. By setting the basis weight of the non-woven fabric layer β to <NUM>/m<NUM>, the smoothness of the non-woven fabric layer B can be improved, and breakage of the non-woven fabric for a sound-absorbing material due to friction between the non-woven fabric for a sound-absorbing material and the mold can be curbed in heating and compression during molding. On the other hand, by setting the basis weight of the non-woven fabric layer β to <NUM>/m<NUM> or less, a non-woven fabric for a sound-absorbing material having excellent lightweight properties can be obtained. From the above viewpoint, the basis weight of the non-woven fabric layer β is preferably <NUM>/m<NUM> or more and <NUM>/m<NUM> or less, and particularly preferably <NUM>/m<NUM> or more and <NUM>/m<NUM> or less.

The tensile elongation at break of the non-woven fabric layer β is preferably <NUM>% or more. By setting the tensile elongation at break to <NUM>% or more, the followability of the non-woven fabric layer β to the mold can be improved, and the breakage of the non-woven fabric layer β can be curbed. From the above point of view, the tensile elongation at break is preferably <NUM>% or more, and more preferably <NUM>% or more. As means for improving the tensile elongation at break of the non-woven fabric layer β, means for improving entanglement between the short fibers contained in the non-woven fabric layer β can be adopted by adjusting the content mass of the short fibers C2 as described above or adopting a needle punching process or a spunlace process in the production of the non-woven fabric layer β. In addition, the tensile elongation at break of the present invention can be measured in accordance with JIS L <NUM>: <NUM><NUM>. <NUM>, and the average value of the tensile elongation at break in a random direction and the tensile elongation at break in a direction orthogonal to the random direction can be calculated and measured.

Next, a preferable production method for producing the non-woven fabric for a sound-absorbing material of the present invention will be described. A preferable method for producing the non-woven fabric of the present invention includes the following processes.

Hereinafter, details of the processes (a) to (g) will be described.

First, the process (opener process) (a) of opening the short fibers A, the short fibers B, and the short fibers C1 will be described. In the opener process, the short fibers A, the short fibers B, and the short fibers C1 (hereinafter also referred to as each short fiber) are weighed such that the contents of the short fibers A, the short fibers B, and the short fibers C1 in the non-woven fabric layer α are as desired, and then each short fiber is sufficiently opened and mixed using air or the like.

Next, the process (carding process) (b) of forming the short fibers A, the short fibers B, and the short fibers C1 into a web will be described. In the carding process, each of the mixed short fibers obtained in the opener process are aligned with a card clothing roller to obtain a web. That is, the web is a film-like sheet made only of fibers, and is also called a fleece.

In the process (c) of opening the short fibers C2 and the other short fibers, similarly to the process (a), the short fibers C2 and the other short fibers are weighed by the opener process, and then the short fibers are sufficiently opened and mixed using air or the like.

In addition, in the process (d) of forming the short fibers C2 and other short fibers into a web, similarly to the process (b), the mixed each short fiber obtained in the opener process is aligned by the card clothing roller in the carding process to obtain a web.

Next, the process (e) of entanglement short fibers C2 with other short fibers by a needle or a water flow to obtain the non-woven fabric layer β (entanglement process) will be described. In the entanglement process, entanglement of short fibers with each other is performed by a mechanical entanglement method using a needle punch method or a water jet punch method (hydroentanglement method). In such an entanglement process, by entangling the short fibers C2 with other short fibers, the tensile elongation at break of the non-woven fabric layer β can be improved, the followability of the non-woven fabric layer β to the mold can be improved, and breakage of the non-woven fabric layer β can be curbed. As the entanglement process, a needle punch method can be preferably employed from the viewpoint of productivity among the above two types. Preferably, by setting the needle density to <NUM> to <NUM> needles/cm<NUM>, the tensile elongation at break of the non-woven fabric layer β can be improved, the followability of the non-woven fabric layer β to the mold can be improved, and breakage of the non-woven fabric layer β can be curbed. By setting the needle density to <NUM> needles/cm<NUM> or more, it is possible to impart entanglement to the non-woven fabric layer β and improve the tensile elongation at break. On the other hand, by setting the needle density to <NUM> needles/cm<NUM> or less, it is possible to curb the yarn breakage of the short fibers by the needle and to improve the tensile elongation at break. In this respect, the needle density is preferably <NUM> to <NUM> needles/cm<NUM>, and particularly preferably <NUM> to <NUM> needles/cm<NUM>.

In the process (f) of layering a web containing the short fibers A, the short fibers B, and the short fibers C1 and the non-woven fabric layer β to obtain a layered web, a method of layering the non-woven fabric layer β while producing a web containing the short fibers A, the short fibers B, and the short fibers C1 is preferably employed.

In the process (g) of melting the short fibers C1 with hot air to obtain the non-woven fabric layer α, and melting the short fibers C2 to fuse the non-woven fabric layer α and the non-woven fabric layer β, the non-woven fabric layer α can be obtained by causing hot air at <NUM> to <NUM> to flow through the layered body from the thickness direction by the thermal bonding method to melt the short fibers C1, and by fusing the non-woven fabric layer α and the non-woven fabric layer β by melting the short fibers C2, the non-woven fabric for a sound-absorbing material of the present invention can be efficiently produced.

Next, the sound-absorbing material will be described. Preferably, a sound-absorbing material containing the non-woven-fabric layered body for a sound-absorbing material of the present invention contains the non-woven-fabric layered body for a sound-absorbing material of the present invention and a non-woven fabric for a skin having an air permeability of <NUM> to <NUM><NUM>/cm<NUM>/s as a skin material, and the non-woven fabric for a skin is layered on a surface side of the non-woven fabric layer α of the non-woven fabric for a sound-absorbing material. Then, the sound-absorbing material having the configuration of skin material/non-woven fabric layer α/non-woven fabric layer β is installed such that the sound incident side becomes the skin material, and accordingly, the sound-absorbing performance of the sound-absorbing material is excellent. By setting the air permeability of the skin material to <NUM><NUM>/cm<NUM>/s or more, sound enters the inside of the sound-absorbing material, and the sound-absorbing performance can be improved by air friction of the skin material and air friction of the non-woven fabric for a sound-absorbing material. On the other hand, when the air permeability of the skin material is <NUM><NUM>/cm<NUM>/s or less, sound-absorbing performance can be improved by resonance between membrane vibration of the skin material and air vibration of the fine porous portion of the non-woven fabric for a sound-absorbing material, which is preferable. From the above point of view, the air permeability of the skin material is preferably <NUM> to <NUM><NUM>/cm<NUM>/s, and particularly preferably <NUM> to <NUM><NUM>/cm<NUM>/s. In addition, the air permeability of the skin material is measured according to JIS L <NUM>-<NUM><NUM>. <NUM>, Method A (Frazier method).

In addition, the preferable configuration as the sound-absorbing material is as described above, but in addition to the non-woven fabric for a skin having the specific air permeability described above, a general needle punch non-woven fabric, a spunlace non-woven fabric, a spunbond non-woven fabric, a melt blown non-woven fabric, a woven or knitted fabric, a fiber board, or a foam can be layered on the surface of the non-woven fabric layer α of the non-woven fabric for a sound-absorbing material and used as a sound-absorbing material as long as the effect of the skin material by the air friction or the resonance action can be obtained.

Hereinafter, evaluation methods and measurement methods used in the present examples will be described.

The non-woven fabric layer α and the non-woven fabric layer β were separated, and regarding each non-woven fabric, based on JIS L <NUM>-<NUM>: <NUM> "Method for Testing Mixing Ratio of Textile Product - Part <NUM>: Differentiation of Fiber" and JIS L <NUM>-<NUM>: <NUM> "Method for Testing Mixing Ratio of Textile Product - Part <NUM>: Fiber Mixing Ratio", the corrected weight mixing ratio (mass ratio of each fiber in the standard state) was measured and used as the content (% by mass) of each fiber constituting the non-woven-fabric layered body for a sound-absorbing material. Thus, the fiber materials constituting the non-woven fabric layer α and the non-woven fabric β of the non-woven-fabric layered body for a sound-absorbing material and the contents (% by mass) thereof were specified.

With respect to the residual non-woven fabric of each of the non-woven fabric layer α and the non-woven fabric layer β in "<NUM>. Dissolution Method" in JIS L <NUM>-<NUM>: <NUM> "Method for Testing Mixing Ratio of Textile Product - Part <NUM>: Fiber Mixing Ratio" of the above (<NUM>), a cross section thereof was observed with a scanning electron microscope (SEM) (S-<NUM> N type manufactured by Hitachi High-Tech Corporation), observation ranges at <NUM> parts were randomly extracted, and a cross-sectional photograph was collected at a magnification of <NUM> times. Further, the diameters of single fibers were measured for all the fibers present in the cross-sectional photograph. At this time, fibers that were fused and fibers that were not fused in the cross-sectional photograph were distinguished. The measurement is performed on fibers that were not fused. In addition, in a case where the cross-sectional shape of the fibers was a modified cross-sectional shape, the cross-sectional area of the fiber was measured from the cross-sectional photograph, and the cross-sectional area was converted into a perfect circle diameter to obtain the single fiber diameter of the fibers. Among the obtained data, single fiber diameter data of fibers that were not fused was distinguished for each section of <NUM>, and the average single fiber diameter for each section and the number of fibers for each section were tabulated. From the obtained average single fiber diameter for each section and the specific gravity of each fiber specified in the above (<NUM>), the fineness of the fibers for each section was calculated by Formula (<NUM>).

For the non-woven fabric layer α, regarding the fibers having a fineness of <NUM> to <NUM> dtex, the content mass (% by mass) of fibers having a fineness of <NUM> to <NUM> dtex was calculated by Formula (<NUM>) from the fineness of fibers in each section, the number of fibers in each section, and the specific gravity of the fiber material. fibers in same section (fibers))/(fineness (dtex) of fibers <MAT>.

Similarly, the content mass (% by mass) of fibers having a fineness of <NUM> to <NUM> dtex was obtained. In addition, the fineness and the content mass (% by mass) of the fiber that were fused were obtained in the same manner. Similarly, for the non-woven fabric layer β, fibers that were fused and fibers that were not fused are distinguished, and the measurement is performed on fibers that were not used. The fineness and the content mass (% by mass) of each fiber were obtained.

In addition, in a case where the non-woven fabric layer α or the non-woven fabric layer β constituting the non-woven fabric for a sound-absorbing material had a plurality of fiber materials, the above measurement of the fineness and the content was performed for each fiber material using the residual non-woven fabric in the dissolution method to obtain the fineness and the content of the fibers constituting the non-woven fabric for a sound-absorbing material.

Each of the non-woven fabric layer α and the non-woven fabric layer β was measured at a temperature rising rate of <NUM>/min under a nitrogen stream using "Shimadzu Differential Scanning Calorimeter: DSC-<NUM>" manufactured by Shimadzu Corporation, and the obtained melting endothermic peak temperature (°C) of the DSC curve was used as the melting point (°C) of the short fibers of respective non-woven fabric layers constituting the non-woven-fabric layered body for a sound-absorbing material. The non-woven fabric layer α and the non-woven fabric layer β contained a plurality of short fibers, and each peak was used as the melting point of the short fibers constituting each non-woven fabric layer. In addition, when the resin was amorphous and a melting endothermic peak could not be confirmed by DSC, the melting start temperature and the melting end temperature were observed at a temperature rising rate of <NUM>/min using a melting point microscope, and the melting point was obtained by Formula (<NUM>).

The basis weight was measured based on JIS L <NUM>: <NUM><NUM>. The non-woven fabric layer α and the non-woven fabric layer β were separated from the non-woven fabric for a sound-absorbing material, and <NUM> test pieces of <NUM> × <NUM> were collected from each sample. The mass of the test piece in the standard state was measured, the basis weight, which is the mass per unit area, was obtained by Formula (<NUM>), and the average value was calculated for each of the non-woven fabric layer α and the non-woven fabric layer β.

In addition, the basis weight of the non-woven fabric for a sound-absorbing material was the total basis weight of the non-woven fabric layer α and the non-woven fabric layer β.

The non-woven fabric layer α and the non-woven fabric layer β were separated from the sample of the non-woven fabric for a sound-absorbing material, and <NUM> test pieces of <NUM> × <NUM> were collected. A ruler was applied to the cross section of the test piece, and the thicknesses of the non-woven fabric layer α and the non-woven fabric layer β were measured. The measurement was performed on each test piece (<NUM> test pieces), and an average value thereof was calculated. In addition, the thickness of the non-woven fabric for a sound-absorbing material was measured as described above without separating the non-woven fabric layer α and the non-woven fabric layer β.

The tensile elongation at break was measured based on JIS L <NUM>: <NUM><NUM>. The non-woven fabric layer β was separated from the non-woven fabric for a sound-absorbing material, and <NUM> test pieces having a width of <NUM> and a length of <NUM> were collected in one random direction.

In addition, <NUM> test pieces having a width of <NUM> and a length of <NUM> were collected in a direction perpendicular to the one random direction. With respect to the obtained test piece (<NUM> pieces in total), a load was applied until the test piece was ruptured under the conditions of a grip interval of <NUM> and a tensile speed of <NUM>/min using a constant-speed extension type tensile tester, and the tensile elongation at break (%) at rupture was measured. The measurement was performed on the <NUM> test pieces, and an average value thereof was calculated. As the evaluation, the higher the tensile elongation at break, the better the molding followability.

The static friction coefficient was measured based on JIS P8147: <NUM><NUM> inclination method. <NUM> test pieces having a width of <NUM> and a length of <NUM> were collected from the non-woven fabric for a sound-absorbing material in any one direction. In addition, <NUM> test pieces having a width of <NUM> and a length of <NUM> were collected in a direction perpendicular to the one random direction. For the obtained test piece (<NUM> pieces in total), the test piece was attached to the inclined plate of the slip inclination angle measuring apparatus such that the long side of the test piece and the long side of the inclined plate were parallel to each other and the non-woven fabric layer β was on the upper surface. Next, a metal weight (width of <NUM>, length of <NUM>, mass of <NUM>) was placed on the test piece such that the long side of the test piece was parallel to the long side of the weight.

In the measurement, the inclined plate was inclined under the condition of an inclination angle of less than <NUM>°/sec, the inclination angle when the weight dropped was read, and the value of the tangent (tanθ) of the inclination angle was collected as the static friction coefficient. The measurement was performed on the <NUM> test pieces, and an average value thereof was calculated. As an evaluation, the smaller the value of the static friction coefficient, the better the smoothness.

From the non-woven fabric for a sound-absorbing material, <NUM> test pieces having a width of <NUM>, a length of <NUM>, and a thickness of <NUM> (a thickness of <NUM> in Comparative Example <NUM>) were collected in any one direction. The end portion of the test piece was fixed with a clamp, and the upper surface and the lower surface of the test piece were heated with a far infrared heater heated to <NUM> until the internal temperature of the non-woven fabric for a sound-absorbing material reached <NUM>. Then, the heated test piece was rapidly moved and pressed between metal plates having a temperature of <NUM> and a size of <NUM> × <NUM> under the conditions of a pressure of <NUM> kPa and a time of <NUM> seconds. The pressed test piece was cut into a size of <NUM> × <NUM>, a metal ruler was applied to the cross section of the test piece, and the thickness (mm) immediately after pressing was measured. The measurement was performed on <NUM> test pieces, and an average value obtained by dividing the measured value by the thickness (mm) before pressing was calculated. The larger the value is, the better the thickness recoverability during molding.

The center of the pressed test piece (<NUM> × <NUM>) prepared in the above (<NUM>) was cut using cutting scissors to have a cutting length of <NUM>, the entire amount of fallen fibers was collected, and the mass (mg) thereof was measured with an electronic balance, and converted to have a cutting length of <NUM> according to the following Formula (<NUM>) to obtain a fiber fall-off amount (mg/m) during cutting. The measurement was performed on <NUM> test pieces, an average value was calculated, and the test pieces were cut. The smaller the value of the fiber fall-off amount during the cutting, the less the fiber fall-off during cutting, which is excellent. fiber fall-off amount during cutting (mg/m) = mass of fallen fiber (mg)/cutting length (m) Formula (<NUM>).

The normal incidence sound absorption coefficient was measured according to the normal incidence sound absorption measurement method (tube method) of JIS A <NUM> (<NUM>). From the pressed test piece (<NUM> × <NUM>) prepared in the above (<NUM>), <NUM> circular test pieces <NUM> having a diameter of <NUM> were collected. Subsequently, <NUM> circular test pieces <NUM> having a diameter of <NUM> were collected from a non-woven fabric for a skin (basis weight: <NUM>/m<NUM>, thickness: <NUM>, Frazier permeability: <NUM><NUM>/cm<NUM>/s) composed of <NUM> dtex polyethylene terephthalate (PET) short fibers (<NUM>% by mass) and <NUM> dtex polyethylene terephthalate (PET) short fibers (<NUM>% by mass). Further, the test piece <NUM> was layered on the surface of the non-woven fabric layer α of the test piece <NUM>.

As the test apparatus, an automatic normal incidence sound absorption coefficient measuring device (model 10041A) manufactured by Electronic Measuring Instruments was used. The test piece was attached to one end of an impedance tube for measurement such that the test piece <NUM> was on the sound incident side, and the normal incidence sound absorption coefficient was measured. As for the sound absorption coefficient for each frequency, a value obtained by multiplying the sound absorption coefficient obtained in the measurement by <NUM> was adopted. Then, the obtained average value of sound absorption coefficient at <NUM> was used as the low-frequency sound absorption coefficient (%), and the obtained average value of sound absorption coefficient at <NUM> was used as the high-frequency sound absorption coefficient (%).

In Example <NUM>, the following non-woven-fabric layered body was used.

Using <NUM>% by mass of short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM> as the short fibers A, <NUM>% by mass of short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM> as the short fibers B, and <NUM>% by mass of core-sheath short fibers (core-sheath ratio of <NUM> : <NUM>) having a fineness of <NUM> dtex and made of polyethylene terephthalate (PET) with a melting point of <NUM> in the core part and crystalline copolymerized polyester with a melting point of <NUM> in the sheath part as the short fibers C1, each short fiber was subjected to an opener process, and then subjected to a carding process to obtain a web.

Using <NUM>% by mass of short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM> as the short fibers, and <NUM>% by mass of core-sheath short fibers (core-sheath ratio of <NUM> : <NUM>) having a fineness of <NUM> dtex and made of polyethylene terephthalate (PET) with a melting point of <NUM> in the core part and amorphous copolymerized polyester with a melting point of <NUM> in the sheath part as the short fibers C2, each short fiber was subjected to an opener process, then subjected to a carding process, and then subjected to a needle punch process (needle density of <NUM> needles/cm<NUM>) to obtain a needle punch non-woven fabric.

The web of the non-woven fabric layer β and the needle punch non-woven fabric of the non-woven fabric layer β were layered, and subjected to a thermal bonding process (hot air temperature: <NUM>) to obtain a non-woven-fabric layered body for a sound-absorbing material having a thickness of <NUM> from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, the content mass ratio of the short fibers A and the short fibers B of <NUM>, the basis weight of <NUM>/m<NUM>, and the thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and the thickness of <NUM>.

In the non-woven-fabric layered body for a sound-absorbing material of Example <NUM>, the tensile elongation at break of the non-woven fabric layer β was high, the followability was excellent, the static friction coefficient of the non-woven fabric for a sound-absorbing material was low, and the smoothness was excellent. In addition, the thickness after pressing was large, the thickness recoverability during molding was excellent, and the fiber fall-off amount during cutting was small, which is good. Furthermore, the layered non-woven fabric for a sound-absorbing material had a high low-frequency sound absorption coefficient and a high high-frequency sound absorption coefficient.

A non-woven fabric for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers A of the non-woven fabric layer α were changed to short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM>. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material of Example <NUM> are shown in Table <NUM>.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers A of the non-woven fabric layer α were changed to short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM>. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers B of the non-woven fabric layer α were changed to short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM>. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers A of Example <NUM> were used as the short fibers A of the non-woven fabric layer α, the short fibers B of Example <NUM> were used as the short fibers B, the short fibers C1 of Example <NUM> were used as the short fibers C1, and each content mass of these short fibers was changed to <NUM>% by mass, <NUM>% by mass, and <NUM>% by mass. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers C1 of the non-woven fabric layer α were changed to core-sheath short fibers (core-sheath ratio of <NUM> : <NUM>) having a fineness of <NUM> dtex and made of polyethylene terephthalate (PET) with a melting point of <NUM> in the core part and crystalline copolymerized polyester with a melting point of <NUM> in the sheath part. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers C1 of the non-woven fabric layer α were changed to core-sheath short fibers (core-sheath ratio of <NUM> : <NUM>) having a fineness of <NUM> dtex and made of polyethylene terephthalate (PET) with a melting point of <NUM> in the core part and amorphous copolymerized polyester with a melting point of <NUM> in the sheath part. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM> were used as the short fibers of the non-woven fabric layer β, the short fibers C2 of Example <NUM> were used as the short fibers C2, and each content mass of these short fibers was changed to <NUM>% by mass and <NUM>% by mass. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the basis weight of the non-woven fabric layer α was changed to <NUM>/m<NUM>. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the basis weight of the non-woven fabric layer α was changed to <NUM>/m<NUM>. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

In the non-woven fabrics for a sound-absorbing material of Examples <NUM> to <NUM>, the tensile elongation at break of the non-woven fabric layer β was high, the followability was excellent, the static friction coefficient of the non-woven fabric for a sound-absorbing material was low, and the smoothness was excellent. In addition, the thickness after pressing was relatively large, the thickness recoverability during molding was excellent, and the fiber fall-off amount during cutting was small, which is good. Furthermore, the layered non-woven fabric for a sound-absorbing material had a high low-frequency sound absorption coefficient and a high high-frequency sound absorption coefficient.

In the non-woven-fabric layered body for a sound-absorbing material of Example, compared to the non-woven-fabric layered body for a sound-absorbing material of Comparative Example <NUM>, due to the effect of the content of the short fibers C2, the tensile elongation at break of the non-woven fabric layer β was higher, the followability was more excellent, the static friction coefficient of the non-woven fabric for a sound-absorbing material was lower, and the smoothness was more excellent. In addition, the thickness after pressing was large, and the thickness recoverability during molding was more excellent due to the effect of the short fibers B in comparison with Comparative Example <NUM>, the effect of the short fibers C1 in comparison with Comparative Example <NUM>, the effect of the content mass ratio of the short fibers A and the short fibers B in comparison with Comparative Example <NUM>, and the effect of the melting point of the sheath part of the short fibers C1 in comparison with Comparative Example <NUM>.

Regarding the fiber fall-off amount during cutting, the fiber fall-off amount was smaller due to the effect of the content of the short fibers C1 in comparison with Comparative Example <NUM> and the effect of the melting point of the sheath part of the short fibers C1 in comparison with Comparative Example <NUM>, which is good.

Furthermore, in comparison with Comparative Examples <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, due to the effects of the fineness, the blending amount, and the blending ratio of the short fibers A and B, and in comparison with Comparative Examples <NUM> and <NUM>, due to the effects of the content of the short fibers C1 and the melting point of the sheath part, a non-woven-fabric layered body for a sound-absorbing material having a high low-frequency sound absorption coefficient and a high high-frequency sound absorption coefficient of the layered non-woven fabric for a sound-absorbing material was obtained. Comparative Examples, whith features not falling under the present invention as specified in claim <NUM>, will be described below.

In the non-woven fabric for a sound-absorbing material of Comparative Example <NUM>, the tensile elongation at break of the non-woven fabric layer β was high, the followability was excellent, the static friction coefficient of the non-woven fabric for a sound-absorbing material was low, and the smoothness was excellent. In addition, the thickness after pressing was large, the thickness recoverability during molding was excellent, and the fiber fall-off amount during cutting was small, which is good. However, the layered non-woven fabric for a sound-absorbing material had a low low-frequency sound absorption coefficient and a low high-frequency sound absorption coefficient.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that <NUM>% by mass of short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM> were used as the short fibers B of the non-woven fabric layer α, <NUM>% by mass of short fibers C1 of Example <NUM> were used as the short fibers C1, and the short fibers A were not used. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. In the non-woven fabric for a sound-absorbing material of Comparative Example <NUM>, the layered non-woven fabric for a sound-absorbing material had a low low-frequency sound absorption coefficient and a low high-frequency sound absorption coefficient.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that <NUM>% by mass of short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM> were used as the short fibers A of the non-woven fabric layer α, <NUM>% by mass of short fibers C1 of Example <NUM> were used as the short fibers C1, and the short fibers B were not used. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. The non-woven fabric for a sound-absorbing material of Comparative Example <NUM> had a small thickness after pressing and poor thickness recoverability during molding, and the layered non-woven fabric for a sound-absorbing material had a low low-frequency sound absorption coefficient and a low high-frequency sound absorption coefficient.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers A of Example <NUM> were used as the short fibers A of the non-woven fabric layer α, the short fibers B of Example <NUM> were used as the short fibers B, the short fibers C1 of Example <NUM> were used as the short fibers C1, and each content mass of these short fibers was changed to <NUM>% by mass, <NUM>% by mass, and <NUM>% by mass. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. The non-woven fabric for a sound-absorbing material of Comparative Example <NUM> had a small thickness after pressing and poor thickness recoverability during molding, and the layered non-woven fabric for a sound-absorbing material had a low low-frequency sound absorption coefficient and a low high-frequency sound absorption coefficient.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers A of Example <NUM> were used as the short fibers A of the non-woven fabric layer α, the short fibers B of Example <NUM> were used as the short fibers B, the short fibers C1 of Example <NUM> were used as the short fibers C1, and each content mass of these short fibers was changed to <NUM>% by mass, <NUM>% by mass, and <NUM>% by mass. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. The non-woven fabric for a sound-absorbing material of Comparative Example <NUM> had a large fiber fall-off amount during cutting and was poor.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers A of Example <NUM> were used as the short fibers A of the non-woven fabric layer α, the short fibers B of Example <NUM> were used as the short fibers B, the short fibers C1 of Example <NUM> were used as the short fibers C1, and each content mass of these short fibers was changed to <NUM>% by mass, <NUM>% by mass, and <NUM>% by mass. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. In the non-woven fabric for a sound-absorbing material of Comparative Example <NUM>, the layered non-woven fabric for a sound-absorbing material had a low low-frequency sound absorption coefficient and a low high-frequency sound absorption coefficient.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers C1 of the non-woven fabric layer α were changed to core-sheath short fibers (core-sheath ratio of <NUM> : <NUM>) having a fineness of <NUM> dtex and made of polyethylene terephthalate (PET) with a melting point of <NUM> in the core part and crystalline copolymerized polyester with a melting point of <NUM> in the sheath part. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. The non-woven fabric for a sound-absorbing material of Comparative Example <NUM> had a small thickness after pressing and poor thickness recoverability during molding, and the layered non-woven fabric for a sound-absorbing material had a low low-frequency sound absorption coefficient and a low high-frequency sound absorption coefficient.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers C1 of the non-woven fabric layer α were changed to core-sheath short fibers (core-sheath ratio of <NUM> : <NUM>) having a fineness of <NUM> dtex and made of polyethylene terephthalate (PET) with a melting point of <NUM> in the core part and crystalline copolymerized polyester with a melting point of <NUM> in the sheath part. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. The non-woven fabric for a sound-absorbing material of Comparative Example <NUM> had a large fiber fall-off amount during cutting and was poor.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM> were used as the short fibers of the non-woven fabric layer β, the short fibers C2 of Example <NUM> were used as the short fibers C2, and each content mass of these short fibers was changed to <NUM>% by mass and <NUM>% by mass. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. In the non-woven fabric for a sound-absorbing material of Comparative Example <NUM>, the static friction coefficient of the non-woven fabric for a sound-absorbing material was high, and the smoothness was poor.

A non-woven-fabric layered body for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM> were used as the short fibers of the non-woven fabric layer β, the short fibers C2 of Example <NUM> were used as the short fibers C2, and each content mass of these short fibers was changed to <NUM>% by mass and <NUM>% by mass. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>. In the non-woven fabric for a sound-absorbing material of Comparative Example <NUM>, the tensile elongation at break of the non-woven fabric layer β was low and the followability was poor.

A non-woven fabric for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the non-woven fabric layer β was not used and the non-woven fabric for a sound-absorbing material composed only of the non-woven fabric layer α was used. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

Since the non-woven fabric for a sound-absorbing material of Comparative Example <NUM> did not use the non-woven fabric layer β, the static friction coefficient was high, smoothness was poor, and during the pressing process, the non-woven fabric partly scraped or broke due to friction with the metal plate. The thickness after pressing was large, the thickness recoverability during molding was excellent, and the fiber fall-off amount during cutting was small, which is good. However, the layered non-woven fabric for a sound-absorbing material had a low low-frequency sound absorption coefficient and a low high-frequency sound absorption coefficient.

A non-woven fabric for a sound-absorbing material was obtained from the non-woven fabric layer α having a content mass of the short fibers A and the short fibers B of <NUM>% by mass, a content mass ratio of the short fibers A and the short fibers B of <NUM>, a basis weight of <NUM>/m<NUM>, and a thickness of <NUM>, and the non-woven fabric layer β having a basis weight of <NUM>/m<NUM> and a thickness of <NUM> under the same processes and conditions as in Example <NUM> except that the short fibers C2 of the non-woven fabric layer β were not used, and the short fibers were changed to <NUM>% by mass of short fibers of polyethylene terephthalate (PET) having a fineness of <NUM> dtex and a melting point of <NUM>. The non-woven fabric layer α and the non-woven fabric layer β were not partially fused. The configuration and evaluation results of the non-woven fabric for a sound-absorbing material are shown in Table <NUM>.

In the non-woven fabric for a sound-absorbing material of Comparative Example <NUM>, since the short fibers C2 were not used, the non-woven fabric layer α and the non-woven fabric layer β were not integrated in the thermal bonding process, and a non-woven-fabric layered body for a sound-absorbing material could not be obtained. In the press working, the non-woven fabric layer α and the non-woven fabric layer β were separated without being integrated, and further, wrinkles were generated on the surface of the non-woven fabric, and the quality was greatly deteriorated. Accordingly, the normal incidence sound absorption coefficient could not be measured.

Claim 1:
A non-woven-fabric layered body for a sound-absorbing material in which a non-woven fabric layer α and a non-woven fabric layer β are layered, wherein
the non-woven fabric layer α contains short fibers A having a fineness of <NUM> to <NUM> dtex, short fibers B having a fineness of <NUM> to <NUM> dtex, and short fibers C1 containing a resin having a melting point of <NUM> to <NUM> in an outer surface layer,
a total content mass of the short fibers A and the short fibers B with respect to a total mass of the non-woven fabric layer α is <NUM> to <NUM>% by mass, a content mass of the short fibers C1 with respect to the total mass of the non-woven fabric layer α is <NUM> to <NUM>% by mass, and a content mass ratio of the short fibers A and the short fibers B (content mass of short fibers A/content mass of short fibers B) is <NUM> to <NUM>,
the non-woven fabric layer β contains short fibers C2 containing a resin having a melting point of <NUM> to <NUM> in an outer surface layer, and a content mass of the short fibers C2 with respect to a total mass of the non-woven fabric layer β is <NUM> to <NUM>% by mass, and
the non-woven fabric layer α and the non-woven fabric layer β are partially fused.