Sound absorbing wall structure

Abstract

To provide a sound absorbing wall structure equipped with a sound absorbing material with low carbon dioxide emissions during manufacturing, etc. and high sound absorption coefficient.SOLUTION: In a sound-absorbing wall structure in which a sound absorbing panel containing a sound absorbing material in a frame is fixed to a wall surface erected along a railroad track or to a post having a pair of flanges facing each other, the sound-absorbing material comprises a wadding material and a skin material encasing the wadding material, the wadding material being a nonwoven fabric containing two or more kinds of thermoplastic resin fibers, in which diameters of the thermoplastic resin fibers differ to each other and the total surface area of an outer diameter of the wadding fibers per unit area of the wadding is 150 to 270 m2 / m2, and the skin material is a nonwoven fabric containing polypropylene resin fibers.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a sound absorbing wall structure. [Background technology]

[0002] There is known a sound absorbing material that is made of a filling material containing fibers made of at least polyester resin and a skin material that contains the filling material, and the skin material is made of a nonwoven fabric containing fibers made of polypropylene resin (see, for example, Patent Document 1). The sound absorbing material is unlikely to lose its sound absorption coefficient even in a moist environment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 251279 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for a sound-absorbing wall structure that has a low amount of carbon dioxide emissions from crude oil extraction to product disposal (hereinafter, also referred to as carbon dioxide emissions during manufacturing, etc. In the case of the present invention, carbon dioxide emissions during manufacturing, etc. refer to the total amount of carbon dioxide emissions during manufacturing from crude oil extraction to sound-absorbing material production and carbon dioxide emissions during sound-absorbing material disposal), and that has a high sound absorption rate. In order to reduce carbon dioxide emissions during manufacturing, etc., it is useful to reduce the amount of resin used as the sound-absorbing material, but simply reducing the amount of resin used tends to reduce the sound-absorbing performance. In addition, it has been found that reducing the amount of resin used generally tends to reduce the rigidity of the sound-absorbing material, causing problems such as the sound-absorbing material being crushed by external pressure, or even if the sound-absorbing material is uniformly arranged during manufacturing, the uniform arrangement cannot be maintained thereafter due to its own weight, resulting in uneven distribution of the resin (filling) in the direction of gravity, and as a result, the sound absorption rate tends to decrease. In addition, sound-absorbing panels fixed to sound-absorbing wall structures are replaced due to deterioration of the sound-absorbing material. In order to reduce carbon dioxide emissions from the manufacture of sound-absorbing panels, it is important to extend the life cycle of the sound-absorbing material in addition to suppressing carbon dioxide emissions during the manufacture of the sound-absorbing panel. It has been found that deterioration of sound-absorbing materials tends to progress when the air space behind the soundproof wall and sound-absorbing material becomes wet.

[0005] Therefore, the problem that the present invention aims to solve is to provide a sound-absorbing wall structure that is equipped with sound-absorbing material that emits little carbon dioxide during manufacturing, has a long replacement cycle due to its improved durability, and has a high sound absorption coefficient. [Means for solving the problem]

[0006] The present inventors have conducted extensive research in light of the above problems and have found that a sound-absorbing material made of a filling material containing a specific nonwoven fabric containing two or more types of thermoplastic resin fibers and a skin material containing the filling emits less carbon dioxide during production and exhibits high sound absorption properties. The present invention has been completed based on these findings.

[0007] The present invention relates to a sound-absorbing wall structure in which a sound-absorbing panel, in which a sound-absorbing material is housed in a frame, is fixed to a wall surface erected along a railway track or to a support having a pair of flanges facing each other, and the sound-absorbing material is made of a filling and a skin material containing the filling, the filling being a nonwoven fabric containing two or more types of thermoplastic resin fibers, the fiber diameters of the thermoplastic resin fibers being different from each other, and the sum of the surface areas of the filling fiber outer diameters per unit area of ​​the filling is 150 to 270 m 2 / m 2 The sound-absorbing wall structure has a surface material that is a nonwoven fabric containing polypropylene-based resin fibers. The total surface area of ​​the outer diameter of the filling fiber per unit area of ​​the filling is preferably 200 to 270 m 2 / m 2 It is. The filling preferably contains at least one thermoplastic resin fiber selected from the group consisting of fine fibers having a fiber diameter of 10 μm or more and less than 20 μm, medium-thick fibers having a fiber diameter of 20 to 30 μm, and extra-thick fibers having a fiber diameter of 40 to 50 μm. The filling more preferably includes at least one thermoplastic resin fiber selected from the group consisting of the medium-thick fibers and the extra-thick fibers, which is a hollow fiber. The filling preferably contains thermoplastic resin hollow fibers, and the content of the thermoplastic resin hollow fibers in the filling is preferably 30% by mass or more. The content of the fine fibers in the filling is preferably 50% by mass or more. The skin material preferably includes a first spunbond nonwoven fabric, a meltblown nonwoven fabric adjacent to the first spunbond nonwoven fabric, and a second spunbond nonwoven fabric adjacent to the meltblown nonwoven fabric.In another embodiment, the skin material preferably includes a first spunbond nonwoven fabric, a meltblown nonwoven fabric adjacent to the first spunbond nonwoven fabric, a second spunbond nonwoven fabric adjacent to the meltblown nonwoven fabric, and a third spunbond nonwoven fabric adjacent to the second spunbond nonwoven fabric. At least one selected from the group consisting of the first spunbond nonwoven fabric, the second spunbond nonwoven fabric, and the third spunbond nonwoven fabric preferably contains fibers having an average fiber diameter in the range of 25 to 50 μm. The meltblown nonwoven fabric preferably contains fibers having an average fiber diameter in the range of 0.5 to 5 μm. At least one selected from the group consisting of the first spunbond nonwoven fabric, the second spunbond nonwoven fabric, and the third spunbond nonwoven fabric preferably contains hollow fibers. The amount of sagging of the filling, as measured by the following test method, is preferably 75 mm or less. The filling, which is 500 mm wide, 1000 mm long, and 50 mm thick, is placed on the top of a desk that is 500 mm or wider and 1000 mm or wider, placed on a level floor, so that the length of the filling is parallel to the length of the desk, the filling is contained within the width of the desk, and the filling extends 600 mm beyond one side of the desk in the length direction, and the distance from the floor to the desk top and the distance from the floor to the bottom of the tip of the filling sample are measured. Sagging amount = Distance from floor to desk top - Distance from floor to bottom of tip of filling sample The carbon dioxide emissions of the skin and the padding, calculated in accordance with the calculation method of the 3R basic unit reported by the Recycling Society Promotion Office, Planning Division, Waste and Recycling Department, Ministry of the Environment, are preferably 8.0 kg / m 2 The following is the result. The clearance between the sound absorbing panel and the sound absorbing wall is preferably 5 to 200 mm. Effect of the Invention

[0008] The sound-absorbing wall structure of the present invention provides a sound-absorbing wall structure which emits less carbon dioxide during production, has a longer replacement cycle due to its improved durability, and is equipped with a sound-absorbing material that exhibits high sound-absorbing properties. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a first embodiment of a sound-absorbing material provided in a sound-absorbing wall structure. [Diagram 2] FIG. 4 is a cross-sectional view of a second embodiment of a sound-absorbing material provided in the sound-absorbing wall structure. [Diagram 3] 1 is a cross-sectional view of one embodiment of an acoustical panel. [Figure 4] FIG. 2 is an explanatory diagram showing one configuration example of the sound absorbing wall structure of the present invention. [Diagram 5] FIG. 4 is an explanatory diagram showing another example of the sound absorbing wall structure of the present invention. [Figure 6] FIG. 4 is an explanatory diagram showing another example of the sound absorbing wall structure of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will now be described in further detail. In addition, unless otherwise specified, "~" in a numerical range means from above to below, and both ends of the range are included. In addition, when a numerical range is indicated, the upper limit and the lower limit can be appropriately combined, and the numerical range obtained by combining them is also disclosed. In addition, in the description of the drawings, the same elements are denoted by the same reference numerals, and duplicated description will be omitted. Also, the dimensional ratios of the drawings are exaggerated for the convenience of explanation, and may differ from the actual ratios.

[0011] Fig. 1 is a cross-sectional view of a first embodiment of a sound-absorbing material provided in a sound-absorbing wall structure of the present invention. The sound-absorbing material 1 of this embodiment is composed of a filling 2 and a single sheet of skin material 3 that is provided on both the front and back sides (upper and lower layers) of the filling 2 and contains the filling 2. The filling 2 is sandwiched between the skin material 3 that is folded in two, and the skin material 3 has seal parts 4 on three sides of its periphery. As a result, the filling 2 is surrounded by the folded parts of the skin material 3 and the seal parts 4, and is contained in the skin material 3.

[0012] It should be noted that the filling 2 needs to be enclosed within the skin material 3, and the configuration in which the filling 2 is enclosed within the skin material 3 is not limited to the configuration shown in FIG.

[0013] For example, as in the second embodiment of the sound-absorbing material provided in the sound-absorbing wall structure of the present invention shown in Figure 2, the sound-absorbing material may be configured to include a filling 2 and two skin materials 3, 3 that are provided on both the front and back sides (upper and lower layers) of the filling 2 and encase the filling 2, and the skin materials 3, 3 have a sealing portion 4 on their peripheral edges that surrounds the filling 2.

[0014] The sound-absorbing material 1 has a weight of 500 to 3000 g / m2, from the viewpoint of improving the sound absorption rate mainly in the 100 to 2000 Hz range, taking into consideration the rolling noise and aerodynamic noise that are the target noise sources under the Shinkansen, and from the viewpoint of preventing a decrease in workability due to an increase in the weight of the sound-absorbing material. 2 The range is preferably 1000 to 2500 g / m 2 More preferably, the range is 1300 to 2200 g / m 2 From the viewpoint of reducing carbon dioxide emissions, the weight per unit area of ​​the sound absorbing material 1 is preferably in the range of 1300 to 1800 g / m 2 In order to ensure the strength of the structure supporting the sound-absorbing material, the weight of the sound-absorbing material 1 is preferably in the range of 1300 to 1700 g / m. 2 It is most preferable that the range is 100%.

[0015] The thickness of the sound-absorbing material 1 is preferably in the range of 10 to 100 mm, and more preferably in the range of 20 to 70 mm, from the viewpoints of further improving the sound absorption coefficient in the low frequency range, particularly in the range of 100 to 1000 Hz, and of ensuring efficient space when installing it in a sound-absorbing wall structure.

[0016] <Padding> The sound-absorbing material of the sound-absorbing wall structure of the present invention comprises a padding, which is a nonwoven fabric containing two or more types of thermoplastic resin fibers, the fiber diameters of which are different from each other.

[0017] The thermoplastic resin constituting the thermoplastic resin fiber is not limited to a specific thermoplastic resin. Examples of the thermoplastic resin include the following thermoplastic resins. (1) Biodegradable resins such as polylactic acid, polyhydroxyalkanoate, polybutylene succinate, cellulose acetate, polyvinyl alcohol, polyglycolic acid, polybutylene succinate-co-adipate, polybutylene adipate terephthalate, and polyethylene terephthalate succinate; (2) Various polyolefin resins such as low density polyethylene, medium density polyethylene, high density polyethylene, ultra-high density polyethylene, polypropylene, polymethylpentene, and copolymers thereof; (3) Chlorine-containing resins such as polyvinyl chloride (PVC) and polyvinylidene chloride (PVdC), (4) Fluorine-containing resins such as tetrafluoroethylene resins, ethylene-tetrafluoroethylene copolymer resins, perfluoroethylenepropene copolymer resins, polychlorotrifluoroethylene resins, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer resins; (5) Addition-type thermoplastic resins other than the addition-type thermoplastic resins shown in (1) to (4), such as ethylene vinyl acetate resin, polymethyl methacrylate (PMMA) resin, polystyrene-based resin, ABS resin, and AS resin. (6) Various polyamide resins such as nylon 6, nylon 66, nylon 12, nylon 11, metaxylylene adipamide (mXD6), hexamethylene terephthalamide (6T), and copolymers thereof; (7) Polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN), polybutylene naphthalate (PBN), polyethylene isophthalate (PEI), polybutylene isophthalate (PBI), polyhexamethylene terephthalate (PHT), polyhexamethylene isophthalate (PHI), polyhexamethylene naphthalate (PHN), polymethylene terephthalate (PMT), polypropylene terephthalate (PPT), Polyesters (excluding biodegradable polyesters) copolymerized with polyethylene-p-oxybenzoate (PEOB), poly-1,4-cyclohexylene dimethylene terephthalate (PCT), and copolymerization components such as diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, and dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, and various polyester-based resins such as liquid crystal polyesters, (8) Condensation thermoplastic resins other than the condensation thermoplastic resins listed in (6) and (7), such as polyamide-imide resin, thermoplastic polyimide, thermoplastic polyurethane, polycarbonate resin, polyacetal (POM) resin, polyetherimide (PEI) resin, polyphenylene ether (PPE) resin, polyether ether ketone (PEEK) resin, and polyphenylene sulfide (PPS) resin.

[0018] As the filling material, for example, a nonwoven fabric containing polyester (polyethylene terephthalate) resin fibers and polypropylene resin fibers can be used.

[0019] The weight of the filling is set to 400 to 2900 g / m from the viewpoint of further improving the sound absorption coefficient mainly in the range of 100 to 2000 Hz and preventing a decrease in workability due to an increase in the weight of the sound absorbing material. 2The range is preferably 900 to 2400 g / m 2 More preferably, the range is 1200 to 2100 g / m 2 From the viewpoint of reducing carbon dioxide emissions, the weight of the filling is preferably in the range of 1200 to 1800 g / m 2 From the viewpoint of ensuring the strength of the padding structure that supports the sound absorbing material, the weight of the padding is particularly preferably in the range of 1200 to 1400 g / m 2 It is most preferable that the range is 1. When the basis weight of the filling is small, the filling (resin) tends to be unevenly distributed due to its own weight, so it is particularly important to set the total surface area of ​​the outer diameter of the filling fibers per unit area, which will be described later, within a predetermined range.

[0020] The polyester (polyethylene terephthalate) resin fiber and the polypropylene resin fiber may be manufactured by a known melt spinning method, or may be purchased from the market. The polyester (polyethylene terephthalate) resin fiber may have an average fiber length in the range of 10 to 100 mm and an average fiber diameter in the range of 10 to 70 μm, for example, and the polypropylene resin fiber may have an average fiber length in the range of 10 to 100 mm and an average fiber diameter in the range of 10 to 50 μm, for example. The fiber diameters of the polyester (polyethylene terephthalate) resin fiber and the polypropylene resin fiber are different.

[0021] From the viewpoint of further improving the sound absorption coefficient, the ratio of polyester-based resin fibers to polypropylene-based resin fibers in the nonwoven fabric molding is preferably, on a mass basis, polyester-based resin fibers:polypropylene-based resin fibers in the range of 99:1 to 5:95, more preferably 95:5 to 10:90, and even more preferably 80:20 to 20:80.

[0022] The nonwoven fabric molding can be obtained, for example, by mixing 1 to 95% by mass, for example 20% by mass, of the polypropylene-based resin fibers, polyester (polyethylene terephthalate) binder fibers using 99 to 5% by mass, for example 30% by mass of a binder resin, and polyester fibers using 99 to 5% by mass, for example 50% by mass of a resin other than the binder resin, forming a web using a fiber spreader and then a carding machine, laminating the obtained web in multiple layers using a cross layer machine, and treating it with a hot air treatment machine set to a predetermined gap distance to fuse the polyester (polyethylene terephthalate) binder fibers and the polypropylene-based resin fibers.

[0023] The polypropylene-based resin may be a homopolymer of propylene, or a copolymer of propylene with other α-olefins copolymerizable with propylene. Examples of the α-olefin include α-olefins having 2 or more carbon atoms, preferably 2 to 8 carbon atoms, such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene. When the polypropylene-based resin is a copolymer of propylene and an α-olefin, it may be a copolymer of one or more α-olefins selected from the α-olefins. The polypropylene-based resin may have an MFR (melt flow rate) in the range of, for example, 1 to 500 g / min.

[0024] The polyester (polyethylene terephthalate) binder fiber may be, for example, one having a polyethylene terephthalate core and a binder component in the sheath. The binder component may be a copolymer polyester made of terephthalic acid or an ester-forming derivative thereof, isophthalic acid or an ester-forming derivative thereof, a lower alcohol, or a polyalkylene glycol or a monoether thereof.

[0025] In order to obtain the effects of the present invention, when combining a plurality of fibers used in the filling, the sum of the surface areas of the outer diameters of the filling fibers per unit area of ​​the plurality of fibers used in the filling is set to a specific range. The sum of the surface areas of the outer diameters of the filling fibers per unit area of ​​the filling is set to 150 to 270 m 2 / m 2 , preferably 200 to 270 m 2 / m 2 The total surface area is 150 m 2 / m 2 If the total surface area is less than 270 m, the sound absorbing properties of the sound absorbing material will be reduced. 2 / m 2 If it is larger, the amount of carbon dioxide emitted during the production of the sound-absorbing material, etc., increases. In order to further improve the sound absorption coefficient mainly in the 100 to 2000 Hz range while reducing the amount of carbon dioxide emitted, it is important to satisfy the above numerical range.

[0026] The total surface area is calculated, for example, as follows. For each fiber constituting the filling, the surface area of ​​the outer diameter of the filling fiber per unit area of ​​the filling is calculated according to the following formula (1), and the sum of all fibers is taken as the total surface area. For hollow fibers, the outer diameter of the fiber cross section (n=10) is measured using an electron microscope, and the average value is calculated. For the denier, the denier value listed in the fiber product specifications is used. Surface area of ​​the outer diameter of the filling fiber per unit area of ​​the filling (m 2 / m 2 ) = fiber diameter (outer diameter μm) / 10 6 ×3.14×9000(m) / denier(g)×weight(g / m 2 )×Content (mass%) / 100...(1)

[0027] In the filling with low carbon dioxide emission, a combination of multiple fibers having a specific fiber diameter produces a better effect. The filling is preferably a nonwoven fabric containing fine fibers having a fiber diameter of 10 μm or more and less than 20 μm, and at least one thermoplastic resin fiber selected from the group consisting of medium-thick fibers having a fiber diameter of 20 to 30 μm and very-thick fibers having a fiber diameter of 40 to 50 μm. The inventors have found that a filling containing at least one fiber selected from the group consisting of the medium-thick fibers and the very-thick fibers in addition to the fine fibers can prevent uneven distribution of the filling (resin) more effectively than a filling containing only the fine fibers. Combining multiple fibers having a specific fiber diameter is useful for obtaining good sound absorption performance in a filling with low carbon dioxide emission. At least one thermoplastic resin fiber selected from the group consisting of the medium-thick fibers and the extra-thick fibers more preferably includes hollow fibers. Hollow fibers tend to have a high degree of fiber orientation and high fiber strength, so that when reducing the basis weight of the sound-absorbing material or the filling, the hollow fibers contribute to ensuring the strength of the filling structure that supports the sound-absorbing material. The present inventors have found that it is particularly preferable to make part of the medium-thick fibers or the extra-thick fibers hollow fibers.

[0028] The filling preferably contains thermoplastic resin hollow fibers, and the content of the thermoplastic resin hollow fibers in the filling is 30% by mass or more. When the content of the thermoplastic resin hollow fibers in the filling is within the above range, the amount of resin used in the sound-absorbing material is reduced. In addition, even if the basis weight of the sound-absorbing material or the filling is reduced, the strength of the filling structure supporting the sound-absorbing material can be ensured.

[0029] The content (total) of the medium-thick fibers and the extra-thick fibers is preferably 25% by mass or more. This ensures the strength of the padding structure that supports the sound-absorbing material and prevents uneven distribution of the padding. The upper limit can be set appropriately depending on the required performance, but from the viewpoint of further improving the sound absorption coefficient, it is preferably less than 60% by mass, and more preferably 50% by mass or less. Furthermore, the content of the fine fibers in the filling is preferably 50% by mass or more and 80% by mass or less. When the content of the fine fibers in the filling is within the above range, all of the following points are satisfied: improving the sound absorption coefficient mainly in the 100 to 2000 Hz range, preventing a decrease in workability due to an increase in the weight of the sound absorbing material, reducing carbon dioxide emissions, and further ensuring the strength of the filling structure supporting the sound absorbing material and the sound absorbing material. From these viewpoints, the content of the fine fibers in the filling is more preferably 55% by mass or more and 75% by mass or less.

[0030] The filling may include composite fibers, non-circular fibers, crimped fibers, split fibers, etc. The filling may also include heat stabilizers, ultraviolet absorbers, weather stabilizers, flame retardants, water repellents, oil agents, antistatic agents, colorants, inorganic substances, etc.

[0031] <Skin material> The skin material is made of a nonwoven fabric containing fibers made of a thermoplastic resin. From the viewpoint of preventing contact between the filling and water, the skin material preferably has a water pressure resistance in the range of 200 to 2000 mmH2O, more preferably has a water pressure resistance in the range of 200 to 500 mmH2O, further preferably has a water pressure resistance in the range of 250 to 450 mmH2O, and particularly preferably has a water pressure resistance in the range of 280 to 400 mmH2O. The water pressure resistance of the skin material can be further increased by at least one method selected from the group consisting of, for example, reducing the average fiber diameter of the fibers constituting the skin material, increasing the density of the skin material, using fibers made of a polypropylene resin, and increasing the basis weight of the skin material. Furthermore, in order to improve the durability of the skin, the back side of the skin, which is prone to deterioration, is protected.

[0032] The air permeability of the skin material is set to 5 to 200 cm from the viewpoint of improving the water pressure resistance to prevent the contact between the padding and water and from the viewpoint of transmitting sound waves appropriately to the padding side to maintain a good sound absorption rate. 3 / cm 2 / sec, and preferably in the range of 7 to 150 cm 3 / cm 2 / sec, more preferably in the range of 10-50 cm 3 / cm 2 More preferably, the range is 1 / second.

[0033] The thickness of the skin material is preferably in the range of 0.1 to 1.5 mm, and more preferably in the range of 0.3 to 1.0 mm, from the viewpoints of further improving the water pressure resistance and further preventing contact between the filling and water, maintaining strength such as shot blast resistance, preventing a situation in which the thickness is so great that sound waves are difficult to transmit to the filling side, and preventing a situation in which the thickness is so great that the workability of ultrasonic sealing, etc. is reduced.

[0034] The average fiber diameter of the fibers located near the surface of the skin material (hereinafter sometimes referred to as surface fiber diameter) is preferably in the range of 10 to 100 μm from the viewpoint of ensuring the strength of the structure supporting the sound absorbing material, and is preferably in the range of 20 to 100 μm, more preferably in the range of 25 to 50 μm, from the viewpoint of further improving shot blast resistance and controlling the air permeability within an appropriate range. Also, from the viewpoint of further improving shot blast resistance, it is particularly preferable that the surface fiber diameter of the fibers made of polypropylene resin is in the above range.

[0035] The polypropylene resin used in the nonwoven fabric constituting the skin material may be a homopolymer of propylene, or a copolymer of propylene and other α-olefins copolymerizable therewith, as in the polypropylene resin used in the filling. As the α-olefin, one or more α-olefins are used, as in the case of the polypropylene resin used in the filling.

[0036] The fibers constituting the skin material may contain heat stabilizers, ultraviolet absorbers, weather stabilizers, flame retardants, water repellents, oil agents, antistatic agents, colorants, inorganic substances, and the like.

[0037] The polypropylene resin used in the nonwoven fabric constituting the skin material may have an MFR (melt flow rate) in the range of, for example, 10 to 100 g / min. In the sound-absorbing material 1, the skin material 3 has a water pressure resistance in the above range, and the inside is sealed with the sealing portion 4, so that the padding 2 does not come into contact with water, and the sound absorption rate is unlikely to decrease even in a humid environment.

[0038] The skin material may be a single layer of nonwoven fabric, or a laminated nonwoven fabric in which a plurality of nonwoven fabrics are laminated. The nonwoven fabric constituting the skin material 3 is not limited to a specific nonwoven fabric, and may be at least one selected from the group consisting of spunbonded nonwoven fabric and meltblown nonwoven fabric. From the viewpoint of further improving the strength such as shot blast resistance as a sound absorbing material, the skin material preferably contains at least one layer of spunbonded nonwoven fabric. Also, from the viewpoint of controlling the water pressure resistance and air permeability within a preferred range, it is preferable to contain at least one layer of meltblown nonwoven fabric. The spunbonded nonwoven fabric and the meltblown nonwoven fabric are distinguished by the average fiber diameter. In an embodiment of the present specification, the average fiber diameter of the spunbonded nonwoven fabric may be in the range of 10 to 100 μm, and the average fiber diameter of the meltblown nonwoven fabric may be in the range of 0.5 to 5 μm.

[0039] The smaller (thinner) the average fiber diameter of the fibers constituting the nonwoven fabric contained in the skin material, the denser the material is and the better its water pressure resistance. On the other hand, from the viewpoint of abrasion resistance (shot blast resistance) against the impact of solid objects such as hail, sleet, and pebbles, it is desirable that the average fiber diameter of the fibers is large (thick). In addition, the average fiber diameter of the fibers contained in spunbond nonwoven fabrics is larger than the average fiber diameter of the fibers contained in meltblown nonwoven fabrics.

[0040] Therefore, the skin material may have at least a three-layer structure (hereinafter, the three-layer structure may be referred to as an SMS structure or a PP-SMS structure) of, for example, a first spunbond nonwoven fabric containing fibers made of a polypropylene resin having an average fiber diameter in the range of 10 to 50 μm, a meltblown nonwoven fabric containing fibers made of a polypropylene resin having an average fiber diameter in the range of 0.5 to 5 μm located on the first spunbond nonwoven fabric, and a second spunbond nonwoven fabric containing fibers made of a polypropylene resin having an average fiber diameter in the range of 10 to 50 μm located on the meltblown nonwoven fabric. The skin material may further include a third spunbond nonwoven fabric containing fibers made of a polypropylene resin having an average fiber diameter in the range of 25 to 50 μm. Alternatively, the skin material may be composed of only one of the spunbond nonwoven fabric layers of the first to third spunbond nonwoven fabrics. Here, "consisting only of a spunbond nonwoven fabric layer" means that it does not include nonwoven fabrics manufactured by other manufacturing methods, such as meltblown nonwoven fabrics, and does not exclude the inclusion of multiple layers of the same or different spunbond nonwoven fabrics.

[0041] When the skin material 3 has a structure of at least three layers, the average fiber diameter of the meltblown nonwoven fabric forming the inner layer is small and dense, thereby ensuring the water pressure resistance within the above range. On the other hand, since the average fiber diameter of the fibers contained in the meltblown nonwoven fabric is small, the meltblown nonwoven fabric may be prone to fluffing and may have poor shot blast resistance, so by using the first or second spunbond nonwoven fabric as the outer layer, the meltblown nonwoven fabric can be protected and tends to have better shot blast resistance.

[0042] Furthermore, the skin material 3 may have at least a four-layer structure (hereinafter, the four-layer structure may be referred to as an SSMS structure or a PP-SMSS structure) including a third spunbond nonwoven fabric containing fibers having an average fiber diameter in the range of 10 to 100 μm located on the second spunbond nonwoven fabric. By providing the third spunbond nonwoven fabric on the outermost surface, the skin material 3 can obtain better shot blast resistance. The third spunbond nonwoven fabric has, for example, an average fiber diameter in the range of 25 to 50 μm and a basis weight of 70 to 150 g / m. 2 From the viewpoints of further improving the sound absorption coefficient mainly in the 100 to 2000 Hz range, preventing a decrease in workability due to an increase in the weight of the sound-absorbing material, reducing carbon dioxide emissions, and further ensuring the strength of the padding structure that supports the sound-absorbing material and the sound-absorbing material, it is preferable to use a third spunbond nonwoven fabric in the above-mentioned range that uses fibers made of a polypropylene-based resin.

[0043] In addition, when the skin material 3 is composed of only a spunbond nonwoven fabric layer, for example, the average fiber diameter is in the range of 10 to 100 μm and the basis weight is in the range of 70 to 200 g / m 2 By including any one of the first to third spunbond nonwoven fabrics in the range, it is possible to achieve both the water pressure resistance and the sound absorption coefficient in the range. The spunbond nonwoven fabric layer may be composed of a single layer or multiple layers of the third spunbond nonwoven fabric, and another spunbond nonwoven fabric may be laminated on the third spunbond nonwoven fabric.

[0044] In addition, when the skin material 3 is composed of only a spunbonded nonwoven fabric layer, the average fiber diameter of the fibers located near the surface (hereinafter, sometimes referred to as the surface fiber diameter) tends to be in the range of 20 to 100 μm, for example, in the range of more than 30 μm and not more than 50 μm, so that excellent shot blast resistance can be obtained. In the spunbonded nonwoven fabric layer, for example, by setting the temperature of the embossing roll in the range of 140 to 170 ° C. and the temperature of the mirror roll in the range of 140 to 170 ° C. and performing embossing (thermocompression processing) to set the welding area ratio to 15% or more, the surface fiber diameter can be set to the above range, and the fusion between fibers in the non-embossed part is promoted, so that the apparent fiber diameter becomes thick. For the same reason, the welding area ratio during embossing can be set to 20% or more, or a large embossing pattern of 0.7 mm square or more can be used even with the same welding area ratio, thereby improving the shot blast resistance.

[0045] The spunbonded nonwoven fabric can be produced using a known spunbonded nonwoven fabric molding machine. More specifically, the spunbonded nonwoven fabric can be produced, for example, by melting a raw material polypropylene resin using an extruder, discharging the molten composition from a plurality of spinnerets, and cooling and stretching the fibrous resin as necessary, and then depositing it on a collecting surface and subjecting it to a heating and pressurizing treatment using an embossing roll.

[0046] The meltblown nonwoven fabric can be produced by using a known meltblown nonwoven fabric molding machine. More specifically, the meltblown nonwoven fabric can be produced by, for example, melting a polypropylene resin as a raw material, discharging it from a spinning nozzle, and pulling it with high-temperature, high-pressure gas to produce polypropylene meltblown fibers, which are then collected and deposited on a collector such as a perforated belt or perforated drum.

[0047] The sealed portion 4 may be formed by thermocompression or ultrasonic sealing. The sealed portion 4 may be formed continuously or discontinuously around the peripheral edge of the skin materials 3, 3 so as to surround the padding 2. When the sealed portion 4 is formed discontinuously, it is preferable that a plurality of parallel sealed portions 4 are formed so that a discontinuous portion of one sealed portion 4 is complemented by a continuous portion of another sealed portion 4.

[0048] The water pressure resistance of the seal portion 4 is not particularly limited as long as the effects of the present invention are achieved, but from the viewpoint of further suppressing water intrusion, it is preferably 100 mmH2O or more, more preferably 150 mmH2O or more, even more preferably 200 mmH2O or more, particularly preferably 250 mmH2O or more, and most preferably 300 mmH2O or more. The upper limit of the water pressure resistance of the seal portion 4 is not particularly limited, but can be, for example, 2000 mmH2O or less, 1000 mmH2O or less, or 500 mmH2O or less.

[0049] The sealing conditions are not particularly limited, but in the case of ultrasonic sealing, they can be arbitrarily adjusted by the pressure during sealing, output voltage, sealing time, sealing pattern, etc. If the seal is too strong, the water pressure resistance tends to decrease, so by appropriately adjusting the above factors, it is possible to maintain the water pressure resistance at a good level.

[0050] The width of the sealed portion 4 is not particularly limited, but is preferably in the range of 0.1 to 5.0 mm from the viewpoint of further improving the water pressure resistance of the sealed portion and suppressing breakage. The width of the sealed portion 4 can be, for example, 0.3 mm.

[0051] In the sound-absorbing material, it is preferable that the sagging amount of the filling material is 75 mm or less, as measured by the following test method, from the viewpoint of reducing carbon dioxide emissions while maintaining sound-absorbing performance. It is useful for the filling material to have a certain degree of rigidity in order to prevent deformation of the sound-absorbing material due to external pressure and to maintain sound-absorbing performance. It is more preferable that the sagging amount is 20 mm or more and 75 mm or less, and more preferably 40 mm or more and 75 mm or less. The inventors have found that when the sagging amount is within the above range, the filling material of the sound-absorbing material can be stored for a long period of time without being unevenly distributed due to its own weight.

[0052] The carbon dioxide emissions of the skin and padding of the sound-absorbing material are 5.0 to 8.0 kg / m, calculated in accordance with the calculation method for the 3R basic unit reported by the Recycling Society Promotion Office, Planning Division, Waste and Recycling Department, Ministry of the Environment. 2 From the viewpoint of reducing carbon dioxide emissions while maintaining sound absorbing performance, it is preferable for the sound absorbing material to be one that satisfies the following requirements.

[0053] <Sound absorbing panel> Next, one embodiment of the sound absorbing panel of the present invention will be described with reference to FIG. 3, the sound-absorbing panel 11 of this embodiment includes a sound-absorbing material 1 and a frame 14 that houses the sound-absorbing material 1. The frame 14 is a box-shaped body that includes a rectangular shielding plate 12 that forms the bottom and side walls 13 that rise from the four sides of the shielding plate 12 and has an open end at the top, and includes a protection panel 15 that is placed at the open end of the frame 14 when the sound-absorbing material 1 is housed in the frame 14, and a support part 16 that is placed on the back surface of the frame 14 and supports the sound-absorbing panel 11 when the sound-absorbing panel 11 is attached to a building or the like.

[0054] The frame 14 may be formed by integrally forming the shielding plate 12, the side wall 13, and the support portion 16, or may be formed by connecting separate members. The material of the frame 14 is not particularly limited as long as it is a material that is durable against weather, moisture, etc., and may be made of metal or resin. As the metal, a lightweight metal such as aluminum or stainless steel is preferably used.

[0055] It is preferable that the protective panel 15 protects the sound absorbing material 1 from solid objects such as hail, sleet, and pebbles while facilitating the penetration of sound waves. For this reason, in this embodiment, a punched plate having a large number of through holes 15a arranged on the surface is preferably used as the protective panel 15, but the protective panel is not limited to a punched plate as long as it protects the sound absorbing material 1 while facilitating the penetration of sound waves. The total area of ​​the through holes 15a relative to the total area of ​​the surface of the protective panel 15 is not particularly limited, but is, for example, in the range of 20% to 80%.

[0056] The material of the protective panel 15 is not particularly limited as long as it can protect the sound absorbing material 1, and is durable against sound wave penetration, weather, moisture, etc., and can be made of metal or resin. As the metal, a lightweight metal such as aluminum or stainless steel is preferably used.

[0057] <Method of manufacturing sound absorbing material> Next, a method for manufacturing the sound-absorbing material 1 of the present embodiment shown in FIG. 1 or FIG. 2 will be described. Examples of methods for fusing the ends include a method in which a heat source such as an iron is applied to heat the resin to melt and then press the resin, an ultrasonic sealing method in which ultrasonic waves are applied to melt the resin while pressing the resin, a laser welding method, a vibration welding method, a high-frequency welding method, and a hot plate welding method. Among these, it is preferable to fuse the ends using the ultrasonic sealing method.

[0058] The fusion temperature is not particularly limited as long as it is a temperature at which the resin of the skin material 3 can be fused, but from the viewpoint of further improving the water pressure resistance and preventing peeling of the fused portion, it is preferably in the range of 130 to 160°C, and more preferably in the range of 140 to 155°C.

[0059] When the fusion step is performed by an ultrasonic sealing method, the output of the ultrasonic sealing device is not particularly limited as long as it can fuse the resin of the skin material 3, but from the viewpoint of further improving the water pressure resistance and suppressing peeling of the fused portion (sealed portion 4), it is preferably in the range of 1 to 5 V. Furthermore, the pressure in the pressure bonding is not particularly limited as long as it can fuse the resin of the skin material 3, but from the viewpoint of further improving the water pressure resistance and suppressing peeling of the fused portion, it is preferably in the range of 0.1 to 5 MPa. Furthermore, the speed at which the fused portion is formed is preferably 1 to 30 m / min from the viewpoint of improving the working efficiency while suppressing peeling of the fused portion.

[0060] <Sound-absorbing wall structure> The sound absorbing wall structure of this embodiment will be described with reference to Figures 4 to 6. The sound absorbing wall structure is preferably for use in railways.

[0061] First, as an example of a sound absorbing wall structure of this embodiment, a structure in which a sound absorbing panel 11 is fixed to a wall surface 20 erected along a railway track will be described as shown in Fig. 4. Incidentally, erecting along a railway track refers to erecting along the railway track within a railway premises.

[0062] Typically, when the sound absorbing panel 11 is fixed to a wall surface 20 made of concrete or the like, an L-shaped joint plate 21 made by bending a metal plate material into an L shape is used.

[0063] The L-shaped joint plate 21 has a flat portion 21a extending from the upper surface of the upper wall 13 or the lower surface of the lower wall 13 of the frame 14 of the sound-absorbing panel 11 to the wall surface 20, and a rising portion 21b that rises vertically at a position where it abuts the wall surface 20.

[0064] The flat plate portion 21a is formed with a width larger than the width of the upper surface of the upper wall 13 or the lower surface of the lower wall 13 of the frame 14 so as to form a gap between the shielding plate 12 on the rear side of the sound-absorbing panel 11 and the wall surface 20. The gap on the rear side of the panel 11 may be structured so that the gap portion is covered with a reinforcing material or the like.

[0065] The flat plate portion 21a is disposed on the upper or lower side of the upper wall 13 of the frame 14 of the sound absorbing panel 11. The L-shaped joint plate 21 has frame connecting holes 22, 22 at positions where it abuts against the lower surface of the wall 13. Fixing screws 23, 23 that are screwed into the upper surface of the upper wall 13 of the frame 14 or the lower surface of the lower wall 13 are inserted into the frame connecting holes 22, 22, and the L-shaped joint plate 21 and the sound-absorbing panel 11 are fastened and fixed by the fixing screws 23, 23.

[0066] The rising portion 21b has a wall connection hole 24, for example at its center position, and an anchor bolt 25 is inserted into the wall connection hole 24 and driven into the wall 20, thereby fastening the L-shaped joint plate 21 and the wall 20 together.

[0067] The driving of the anchor bolt 25 into the wall surface 20 may be achieved by embedding an anchor in the wall surface 20 in advance and fastening the anchor bolt 25 to the anchor, or it may be achieved by fastening a no-plug anchor bolt 25, which does not require an anchor, directly to the wall surface 20.

[0068] In addition, when the sound-absorbing panel 11 is divided vertically into multiple tiers, an L-shaped joint plate 21 may be provided on the upper surface of the upper wall 13 of the topmost sound-absorbing panel 11 and on the lower surface of the lower wall 13 of the bottommost sound-absorbing panel 11, and the sound-absorbing panels 11 in the middle tier may be connected to each other by a connecting member that connects the upper and lower sound-absorbing panels.

[0069] Furthermore, the fastening position between the sound-absorbing panel 11 and the wall surface 20 by the L-shaped joint plate 21 may be, in addition to or instead of the upper surface of the upper wall 13 of the sound-absorbing panel 11 or the lower surface of the lower wall 13 of the sound-absorbing panel 11, the left and right side surfaces of the left and right side walls 13 of the sound-absorbing panel 11. The clearance between the sound absorbing panel 11 and the wall surface 20 is preferably 5 to 200 mm, more preferably 30 to 150 mm, and further preferably 50 to 100 mm.

[0070] Next, another example of the sound absorbing wall structure of this embodiment shown in FIG. 5 will be described.

[0071] When the sound-absorbing panel 11 is fixed to a pillar 30 erected along a railway track, an S-shaped joint plate 31 (corresponding to the interposition member of the present invention) made by bending a metal plate into an S shape is used. Note that the pillar 30 is not limited to an H-shaped steel having two pairs of flanges 30a, 30a, but it is sufficient if it has at least one pair of flanges 30a, 30a.

[0072] The S-shaped joint plate 31 has a first planar portion 31a that is parallel to and abuts the front surface 15 of the sound-absorbing panel 11, a second planar portion 31b that is parallel to and abuts the flange a, and a vertical surface portion 31c that connects the first planar portion 31a and the second planar portion 31b by a plane that is perpendicular to each other.

[0073] A through hole (not shown) is formed in the first flat portion 31a so that the first flat portion 31a and the side wall 13 (more precisely, the front surface of the upper wall 13) of the sound-absorbing panel 11 are pierced simultaneously at a position where the first flat portion 31a and the side wall 13 of the sound-absorbing panel 11 are aligned, and the S-shaped joint plate 31 and the sound-absorbing panel 11 are fastened and fixed together by screwing a bolt 32 inserted through the through hole into a nut (not shown) provided on the side wall 13 side.

[0074] A through hole (not shown) is formed in the second flat portion 31b so that the second flat portion 31b and the flange 30a of the pillar 30 are passed through the two plates at the same time at a mating position, and a bolt (not shown) provided on the flange 30a side is inserted into the through hole and a nut 33 is screwed into the bolt, thereby fastening the S-type joint plate 31 and the pillar 30 together.

[0075] The S-shaped joint plate 31 may be fastened to the side walls 13 of the sound-absorbing panel 11 at the left and right side walls 13 in addition to or instead of the upper side wall 13 of the sound-absorbing panel 11 .

[0076] Next, another example of the sound absorbing wall structure of this embodiment shown in FIG. 6 will be described. The fixing structure between the flange 30a of the pillar 30 and the sound-absorbing panel 11 may be configured by interposing a leaf spring 40 (corresponding to the interposing member of the present invention) formed by bending a steel plate between the flange 30a. In this case, the leaf spring 40 is provided on the outside of the pillar 2 (the side opposite the railway track).

[0077] The leaf spring 40 includes a U-shaped clamping portion 41 that clamps both the inner and outer surfaces of one end of a metal plate member 50 having an extended flange 30a. The clamping portion 41 is configured by an outer piece 41a and an inner piece 41b that face each other.

[0078] The clamping portion 41 has an insertion hole (not shown) formed in each of the outer piece 41a and the inner piece 41b, and the advance / retract bolt 42 is inserted into the insertion hole when the advance / retract bolt 42 is screwed into the screw hole 43 of the plate member 50.

[0079] An abutting piece 44 that abuts against the frame 12 of the sound absorbing panel 11 is connected to the inner piece 41b of the clamping portion 41. The abutting piece 44 extends by folding back to the side facing the inner piece 41b.

[0080] Furthermore, an input portion 45 is connected to the contact piece 44 and is folded back toward the space between the inner piece 41b and the contact piece 44. The input portion 45 is brought into contact with the tip of the advance / retract bolt 42 which is screwed into the plate member 50.

[0081] A tapered projection 42a is formed at the tip of the retractable bolt 42. A receiving hole (not shown) into which the projection 42a at the tip of the retractable bolt 42 fits is formed in the input portion 45 of the leaf spring 40, which is an intermediate member.

[0082] In such a configuration, the advance / retract bolt 42 is screwed into the plate member 50, and by simply rotating the head 42b of the advance / retract bolt 42, the advance / retract bolt 42 advances and retreats, and the tip of the advance / retract bolt 42 can be pressed against the input portion 45 at a fixed position, so that the pressing force of the advance / retract bolt 42 can be reliably transmitted to the abutment piece portion 44.

[0083] In this embodiment, the flange 30a is extended by the plate member 50, i.e., the flange 30a and the plate member 50 are fastened by the fastening bolts 51 and the nuts 52. However, this is not limited to this, and the plate member 50 may be omitted and the leaf spring 40 may be directly attached to the flange 30a. EXAMPLES

[0084] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0085] In the examples and comparative examples, various physical properties were measured or calculated as follows. (1) Weight Five 10 cm square samples were taken from the sound absorbing material, not including the side surfaces. The mass of each sample (sound absorbing material and padding) was then measured, and the total mass was divided by the total area to obtain the basis weight (g / m 2 ) was calculated.

[0086] (2) Average fiber diameter For the spunbond nonwoven fabric, ten test pieces of 10 mm x 10 mm were taken, and the diameters of 20 arbitrary points for each test piece were read in μm units to the first decimal place at a magnification of 50 times using a microscope (Nikon Corporation, product name: ECLIPSE E400), and the average value was taken as the average fiber diameter.For the meltblown nonwoven fabric, the fiber diameters (μm) of 30 constituent fibers of the taken sample pieces were measured at a magnification of 500 times or 1000 times using a scanning electron microscope (Hitachi, Ltd., model name: SU3500), and the average value was taken as the average fiber diameter.

[0087] (3) The sum of the surface areas of the outer diameters of the filling fibers per unit area of ​​the filling For each fiber constituting the filling, the surface area of ​​the outer diameter of the filling fiber per unit area of ​​the filling was calculated according to the following formula (1), and the total of all fibers was taken as the total surface area. For hollow fibers, the outer diameter of the fiber cross section (n=10) was measured using an electron microscope and the average value was calculated. For the denier, the denier value listed in the fiber product specifications was used. Surface area of ​​the outer diameter of the filling fiber per unit area of ​​the filling (m 2 / m 2 ) = fiber diameter (outer diameter μm) / 10 6 ×3.14×9000(m) / denier(g)×weight(g / m 2 )×Content (mass%) / 100...(1)

[0088] (4) Sound absorption coefficient According to JIS A 1405-2 (transfer function method), a thick tube with an inner diameter of 100 mm was used as the thick tube, and a thin tube with an inner diameter of 29 mm was used as the thin tube to measure the normal incidence sound absorption coefficient. SMS structure nonwoven fabric or SSMS structure nonwoven fabric (in this case, SSMS structure nonwoven fabric laminated with the third spunbond nonwoven fabric side facing outward) was placed on both sides of the padding cut to the specified size, and the measurement was performed. Note that the sound absorption coefficient at 1 / 3 octave band center frequencies of 125 to 1000 Hz was measured using a thick tube, and the sound absorption coefficient at 1250 to 6300 Hz was measured using a thin tube.

[0089] (5) Carbon dioxide emissions The calculation was performed according to the calculation method of the 3R basic unit reported by the Recycling Society Promotion Office, Planning Division, Waste and Recycling Department, Ministry of the Environment (see https: / / www.env.go.jp / press / files / jp / 19747.pdf). Here, the recycled fiber in the present invention is treated as a concept that includes reused fibers, and the carbon dioxide emission from the crude oil extraction of the recycled fiber to the resin production was calculated as zero. In addition, from the viewpoint of precisely evaluating the reduction rate of carbon dioxide emission, the carbon dioxide emission from the resin to the production of the sound-absorbing material was calculated using the data of the public reference numbers JP212022 and JP212024 of the "Carbon Footprint System Trial Project CO2 Equivalent Common Basic Unit Database ver.4.01 (Domestic Data)" for nonwoven fabrics containing polypropylene-based resin fibers and polyolefin fibers, and polyester (polyethylene terephthalate)-based fibers, respectively. In addition, the carbon dioxide emission that may occur in the process of manufacturing the sound-absorbing material was not taken into consideration and was set to zero. The carbon dioxide emissions from crude oil extraction to resin production per 1 kg of nonwoven fabric and polyolefin fiber containing polypropylene resin fiber were calculated as 1.49 kg, and the carbon dioxide emissions from crude oil extraction to resin production per 1 kg of polyester (polyethylene terephthalate) fiber were calculated as 1.59 kg. Sound-absorbing material was disposed of by incineration, and the carbon dioxide emissions from incineration per 1 kg of nonwoven fabric and polyolefin fiber containing polypropylene resin fiber were calculated as 3.14 kg, and the carbon dioxide emissions from incineration per 1 kg of polyester (polyethylene terephthalate) fiber were calculated as 2.29 kg. GHG (Greenhouse Gas) emissions were calculated as carbon dioxide emissions. "Calculated in accordance with the calculation method for the 3R basic unit reported by the Recycling Society Promotion Office, Planning Division, Waste Management and Recycling Department, Ministry of the Environment" means that the calculation includes these prerequisites. An example of calculating carbon dioxide emissions is described below.

[0090] (6) Amount of sagging padding A piece of filling measuring 500 mm wide x 1000 mm long x 50 mm thick was placed on the top of a desk measuring 500 mm or more wide x 1000 mm or more long, which was placed on a level floor, so that the length of the filling was parallel to the length of the desk, the filling was contained in the width direction of the desk, and the filling extended 600 mm on one side of the length of the desk, and the distance from the floor to the desk top and the distance from the floor to the bottom surface of the tip of the filling sample were measured, and the amount of sagging of the filling was calculated using the following formula (2). Amount of sagging = Distance from floor to desk top - Distance from floor to bottom of tip of filling sample (2)

[0091] (7) Uneven distribution of filling Sound-absorbing material measuring 250mm wide x 250mm long x 50mm thick was prepared and placed vertically between the walls spaced 60mm apart. In this state, when visually inspecting the top surface, if it was found to be not rectangular but had a mountain shape, it was determined that the filling was unevenly distributed.

[0092] (8) Hollow ratio of hollow fibers in spunbond nonwoven fabrics The hollow fibers of the spunbonded nonwoven fabric were embedded in epoxy resin and then cut with a microtome to obtain a sample piece, which was observed under an electron microscope (manufactured by Hitachi, Ltd., model name: SU3500) to obtain the cross-sectional area of ​​the entire fiber and the cross-sectional area of ​​the central part in the cross-sectional image of the fiber, and calculated using the following formula. Hollow ratio [%] = (cross-sectional area of ​​hollow part / cross-sectional area of ​​entire fiber) × 100 (2) The hollowness ratio was calculated as the average value of measurements of 100 fibers.

[0093] The fibers that make up the filling are as follows: Fiber 1: Solid short fiber of propylene-based polymer (manufactured by Ube Exsymo Co., Ltd., product name: UC Fiber, average fiber diameter 21 μm, 2 denier, average fiber length 51 mm) Fiber 2: Solid short fiber of polyethylene terephthalate resin as binder fiber (manufactured by Unitika Ltd., product name: Melty 4080, 2 denier, average fiber diameter 14 μm, average fiber length 51 mm) Fiber 3: Solid short fiber of polyethylene terephthalate resin (average fiber diameter 14 μm, 2 denier, average fiber length 51 mm) Fiber 4-1: Solid short fiber of polyethylene terephthalate resin (average fiber diameter 14 μm, 2 denier, average fiber length 51 mm) Fiber 4-2: Solid short fiber of polyethylene terephthalate resin (average fiber diameter 14 μm, 2 denier, recycled fiber, average fiber length 51 mm) Fiber 5: Solid short fiber of polyethylene terephthalate resin (average fiber diameter 25 μm, 6 denier, average fiber length 51 mm) Fiber 6: Polyethylene terephthalate resin hollow short fiber (average fiber diameter 21 μm, 6 denier, hollow ratio 28%, average fiber length 51 mm) Fiber 7: Polyethylene terephthalate resin hollow short fiber (average fiber diameter 45 μm, 14 denier, hollow ratio 28%, recycled fiber, average fiber length 51 mm) Fiber 8: Recycled solid short fiber made of polyethylene terephthalate resin (average fiber diameter 45 μm, 20 denier, average fiber length 51 mm)

[0094] [Example 1] <Preparation of skin material> A propylene homopolymer with an MFR of 60 g / 10 min was used to perform melt spinning at 230°C by a conventional spunbond method using a spunbond nonwoven fabric molding machine with a spinneret with a diameter of 0.6 mm. The fibers obtained by spinning were deposited on a collection surface, and the average fiber diameter was 13 μm and the basis weight was 10 g / m. 2 A first spunbond nonwoven fabric was obtained. Next, a propylene homopolymer having an MFR of 400 g / 10 min was melted at 280° C. using an extruder, and the resulting melt was discharged from a spinneret while being blown with heated air at 280° C. by a conventional melt-blowing method to deposit fibers having an average fiber diameter of 3 μm on the first spunbond nonwoven fabric, resulting in a basis weight of 5 g / m 2 A meltblown nonwoven fabric was formed. Next, fibers were deposited on the meltblown nonwoven fabric in the same manner as the spunbond nonwoven fabric, resulting in an average fiber diameter of 13 μm and a basis weight of 10 g / m 2 A second spunbond nonwoven fabric was formed. Next, the laminate in which the first spunbond nonwoven fabric, the meltblown nonwoven fabric, and the second spunbond nonwoven fabric were laminated in this order was integrated by a hot embossing roll with an imprint area ratio of 18%, with the embossing roll temperature set at 145°C and the mirror roll at 150°C, to obtain a three-layer structure (SMS structure) nonwoven fabric in which the first spunbond nonwoven fabric and the second spunbond nonwoven fabric were laminated on both the front and back sides of the meltblown nonwoven fabric. The basis weight of the obtained SMS structure nonwoven fabric was 25 g / m 2 It was. Next, a propylene homopolymer having an MFR of 60 g / 10 min was used to perform melt spinning by a conventional spunbonding method at 230° C. in a spunbonding nonwoven fabric molding machine having a spinneret with a diameter of 1.3 mm, and the fibers obtained by spinning were deposited on the SMS structure nonwoven fabric to obtain a fiber having an average fiber diameter of 35 μm and a basis weight of 100 g / m. 2 A third spunbond nonwoven fabric was formed. Next, the laminate of the SMS nonwoven fabric and the spunbond nonwoven fabric in contact with the second spunbond nonwoven fabric side of the SMS nonwoven fabric was integrated with a hot embossing roll (embossed pattern 0.9 mm square) with an imprint area ratio of 18% and an embossing roll temperature of 155°C and a mirror roll temperature of 160°C, to obtain a four-layered (SSMS) nonwoven fabric in which the spunbond nonwoven fabric was laminated on the SMS nonwoven fabric as a skin material. The basis weight of the SSMS nonwoven fabric was 125 g / m 2 , carbon dioxide emissions are 0.7 kg / m 2 The carbon dioxide emissions from the SSMS structure nonwoven fabric were calculated as follows based on the carbon dioxide emissions from crude oil extraction to resin production per 1 kg of the nonwoven fabric containing polypropylene-based resin fiber and polyolefin fiber, the carbon dioxide emissions per 1 kg of the nonwoven fabric containing polypropylene-based resin fiber when incinerated, and the public reference number JP212022 of the "Carbon Footprint System Pilot Project CO2 Equivalent Common Basic Unit Database ver. 4.01 (Domestic Data)".

[0095] <Calculating carbon dioxide emissions from covering materials using polypropylene-based fibers> The carbon dioxide emissions from the covering material using polypropylene-based fibers were calculated as follows. (Carbon dioxide emissions from skin material using polypropylene-based fiber) = [(Carbon dioxide emissions from crude oil extraction to resin production per 1 kg of nonwoven fabric containing polypropylene-based resin fiber) + (Carbon dioxide emissions at incineration per 1 kg of nonwoven fabric containing polypropylene-based resin fiber) + (Carbon dioxide emissions based on the public reference number JP212022 of the "Carbon Footprint System Pilot Project CO2 Equivalent Common Basic Unit Database ver. 4.01 (Domestic Data))] x basis weight / 1000···(3)

[0096] <Making the filling> 5 parts by mass of fiber 1, 30 parts by mass of fiber 6, 30 parts by mass of fiber 8, and 35 parts by mass of fiber 3 were mixed and formed into a web using a fiber spreader and then a carding machine. The web was then multi-layered using a cross-layer machine and treated using a hot air treatment machine with a gap distance set to about 50 mm to obtain a sheet-like nonwoven fabric molding having a thickness of about 50 mm, which contained short fibers of a propylene-based polymer and short fibers of a polyethylene terephthalate-based resin.

[0097] <Production of sound-absorbing material> The batting was cut to 250 mm (length) x 250 mm (width) x 49 mm (thickness). Next, the SSMS structure nonwoven fabric was placed on both sides of the cut batting so that the third spunbond nonwoven fabric side was the outermost surface, and the peripheral portion of the SSMS structure nonwoven fabric around the batting was fused with an ultrasonic sealer (manufactured by Seidensha Denshi Kogyo Co., Ltd., product name: JII430SA) under conditions of output 2.0 V, pressure 0.3 MPa, and speed 5 m / min to form a continuous seal portion with a width of 0.3 mm, thereby obtaining a sound absorbing material in which the batting was encapsulated in the SSMS structure nonwoven fabric. The excess portion on the outer periphery of the seal portion was cut off and removed.

[0098] The physical properties and performance of the sound absorbing material were measured or calculated. The results are shown in Table 1. The "CO2 emission of the filling" in Table 1 is calculated as follows based on the public reference numbers JP212022 and JP212024 of the "Carbon Footprint System Trial Project CO2 Equivalent Common Basic Unit Database ver. 4.01 (Domestic Data)" based on the carbon dioxide emission amount per 1 kg of the polypropylene resin fiber from crude oil extraction to resin production, the carbon dioxide emission amount per 1 kg of the polyester (polyethylene terephthalate) resin fiber from crude oil extraction to resin production, the carbon dioxide emission amount per 1 kg of the polypropylene resin fiber during incineration, the carbon dioxide emission amount per 1 kg of the polyester (polyethylene terephthalate) resin fiber from crude oil extraction to resin production.

[0099] <Calculation of carbon dioxide emissions from filling made of polypropylene-based fiber and polyester (polyethylene terephthalate)-based resin fiber> The carbon dioxide emissions from filling made of polypropylene-based fibers and polyester (polyethylene terephthalate)-based resin fibers were calculated as follows. (Carbon dioxide emissions from filling using polypropylene-based fiber and polyester (polyethylene terephthalate)-based resin fiber) = [(Carbon dioxide emissions from crude oil extraction to resin production per 1 kg of the polypropylene-based resin fiber) + (Carbon dioxide emissions at incineration per 1 kg of the polypropylene-based resin fiber) + (Carbon dioxide emissions based on the public reference number JP212022 of the "Carbon Footprint System Pilot Project CO2 Equivalent Common Basic Unit Database ver. 4.01 (Domestic Data))] × Basis weight of filling × [Content of polypropylene-based resin fiber in filling (mass%)] / 1000 + [(carbon dioxide emissions from crude oil extraction to resin production per 1 kg of the polyester (polyethylene terephthalate) resin fiber) + (carbon dioxide emissions at incineration per 1 kg of the polyester (polyethylene terephthalate) resin fiber) + (carbon dioxide emissions based on the public reference number JP212024 of the "Carbon Footprint System Trial Project CO2 Equivalent Common Basic Unit Database ver. 4.01 (Domestic Data))] x basis weight of batting x [content of polyester (polyethylene terephthalate) resin fiber in batting (mass%)] / 1000 ··· (4)

[0100] [Examples 2 to 12] and [Comparative Examples 1 to 5] Sound-absorbing materials were prepared in the same manner as in Example 1, except that the fibers used in the preparation of the padding were changed as shown in Tables 1 to 3, and the physical properties and performance of the sound-absorbing materials were measured or calculated. The results are shown in Tables 1 to 3.

[0101] [Example 13] <Preparation of skin material> A propylene homopolymer with an MFR of 60 g / 10 min was used to perform melt spinning at 230°C by a conventional spunbond method using a spunbond nonwoven fabric molding machine with a spinneret with a diameter of 0.6 mm. The fibers obtained by spinning were deposited on a collection surface, and the average fiber diameter was 13 μm and the basis weight was 10 g / m. 2 A first spunbond nonwoven fabric was obtained. Next, a propylene homopolymer having an MFR of 400 g / 10 min was melted at 280° C. using an extruder, and the resulting melt was discharged from a spinneret while being blown with heated air at 280° C. by a conventional melt-blowing method to deposit fibers having an average fiber diameter of 3 μm on the first spunbond nonwoven fabric, resulting in a basis weight of 5 g / m 2 A meltblown nonwoven fabric was formed. Next, fibers were deposited on the meltblown nonwoven fabric in the same manner as the spunbond nonwoven fabric, resulting in an average fiber diameter of 13 μm and a basis weight of 10 g / m 2 A second spunbond nonwoven fabric was formed. Next, the laminate in which the first spunbond nonwoven fabric, the meltblown nonwoven fabric, and the second spunbond nonwoven fabric were laminated in this order was integrated by a hot embossing roll with an imprint area ratio of 18%, with the embossing roll temperature set at 145°C and the mirror roll at 150°C, to obtain a three-layer structure (SMS structure) nonwoven fabric in which the first spunbond nonwoven fabric and the second spunbond nonwoven fabric were laminated on both the front and back sides of the meltblown nonwoven fabric. The basis weight of the obtained SMS structure nonwoven fabric was 25 g / m 2 It was. Next, a propylene homopolymer having an MFR of 60 g / 10 min was used to perform melt spinning at 230° C. by a conventional spunbonding method in a spunbonding nonwoven fabric molding machine having a spinneret with a hole shape as shown in FIG. 4 and a cross section of a substantially circular hollow shape, and the fibers obtained by spinning were deposited on the SMS structure nonwoven fabric to form a fiber having an average fiber diameter of 40 μm, a hollow ratio of 16%, and a basis weight of 100 g / m 2 A third spunbond nonwoven fabric was formed. Next, the laminate of the SMS nonwoven fabric and the spunbond nonwoven fabric in contact with the second spunbond nonwoven fabric side of the SMS nonwoven fabric was integrated with a hot embossing roll (embossed pattern 0.9 mm square) with an imprint area ratio of 18% and an embossing roll temperature of 155°C and a mirror roll temperature of 160°C, to obtain a four-layered (SSMS) nonwoven fabric in which the spunbond nonwoven fabric was laminated on the SMS nonwoven fabric as a skin material. The basis weight of the SSMS nonwoven fabric was 125 g / m 2 , carbon dioxide emissions are 0.7 kg / m 2The carbon dioxide emissions from the SSMS structure nonwoven fabric were calculated as follows based on the carbon dioxide emissions from crude oil extraction to resin production per 1 kg of the nonwoven fabric containing polypropylene-based resin fiber and polyolefin fiber, the carbon dioxide emissions per 1 kg of the nonwoven fabric containing polypropylene-based resin fiber when incinerated, and the public reference number JP212022 of the "Carbon Footprint System Pilot Project CO2 Equivalent Common Basic Unit Database ver. 4.01 (Domestic Data)". A sound-absorbing material was prepared in the same manner as in Example 1, except that the fibers used in preparing the skin and the padding were changed as shown in Table 2, and the physical properties and performance of the sound-absorbing material were measured or calculated. The results are shown in Table 2.

[0102] [Example 14] A sound-absorbing material was prepared in the same manner as in Example 13, except that the fibers used in the preparation of the padding were changed as shown in Table 2, and the physical properties and performance of the sound-absorbing material were measured or calculated. The results are shown in Table 2.

[0103] [Example 15] The basis weight of the third spunbond nonwoven fabric of Example 13 was 80 g / m 2 A sound-absorbing material was prepared in the same manner as in Example 13, except that the fibers used in the preparation of the padding were changed as shown in Table 3, and the physical properties and performance of the sound-absorbing material were measured or calculated. The results are shown in Table 3.

[0104] [Table 1]

[0105] [Table 2]

[0106] [Table 3]

[0107] The sound absorbing panels of Comparative Examples 1 to 3, in which the sum of the surface areas of the outer diameters of the filling fibers per unit area of ​​the filling was too small, had low sound absorption coefficients. The sound absorbing panels of Comparative Examples 4 and 5, in which the sum of the surface areas of the outer diameters of the filling fibers per unit area of ​​the filling was too large, had very low sound absorption coefficients, the filling was unevenly distributed, and the carbon dioxide emissions were high. On the other hand, the sound absorbing panels of Examples 1 to 15 had high sound absorption coefficients, the carbon dioxide emissions of the resins constituting these sound absorbing panels were small, and the filling they contained was not unevenly distributed. [Explanation of symbols]

[0108] 1...sound absorbing material, 2...filling, 3...skin material, 4...sealing portion, 11...sound absorbing panel, 12...shielding plate, 13...side wall, 14...frame, 15...protective panel, 16...support portion, 20...wall surface (concrete wall), 21...L-shaped joint plate, 21a...flat plate portion, 21b...rising portion, 30...support, 30a...flange, 31...S-shaped joint plate, 31a...first planar portion, 31b...second planar portion, 31c...vertical surface portion, 40...leaf spring, 41...clamping portion, 42...advance / retract bolt, 44...contact piece portion, 45...input portion, 50...plate member.

Claims

1. A sound-absorbing wall structure in which a sound-absorbing panel having a sound-absorbing material housed in a frame is fixed to a wall surface erected along a railway track or to a support having a pair of flanges facing each other, The sound absorbing material is made of a padding and a skin material containing the padding, The filling is a nonwoven fabric containing two or more types of thermoplastic resin fibers, The fiber diameters of the thermoplastic resin fibers are different, The total surface area of ​​the outer diameter of the filling fiber per unit area is 150 to 270 m ２ / m ２ and The sound-absorbing wall structure has a surface material that is a nonwoven fabric containing polypropylene-based resin fibers.

2. In the sound absorbing wall structure according to claim 1, the sum of the surface areas of the outer diameters of the filling fibers per unit area of ​​the filling is 200 to 270 m ２ / m ２ This is a sound-absorbing wall structure.

3. 2. The sound absorbing wall structure according to claim 1, wherein the filling is a nonwoven fabric containing at least one thermoplastic resin fiber selected from the group consisting of fine fibers having a fiber diameter of 10 μm or more and less than 20 μm, medium-thick fibers having a fiber diameter of 20 to 30 μm, and extra-thick fibers having a fiber diameter of 40 to 50 μm.

4. 4. The sound absorbing wall structure according to claim 3, wherein said filling comprises at least one thermoplastic resin fiber selected from the group consisting of said medium-thick fibers and said extra-thick fibers, said thermoplastic resin fiber including hollow fibers.

5. 2. The sound absorbing wall structure according to claim 1, wherein the filling contains thermoplastic resin hollow fibers, and the content of the thermoplastic resin hollow fibers in the filling is 30% by mass or more.

6. 4. The sound absorbing wall structure according to claim 3, wherein the content of said fine fibers in said padding is 50% by mass or more.

7. 2. The sound absorbing wall structure according to claim 1, wherein the skin material is a skin material comprising a first spunbond nonwoven fabric, a meltblown nonwoven fabric adjacent to the first spunbond nonwoven fabric, and a second spunbond nonwoven fabric adjacent to the meltblown nonwoven fabric, or a skin material comprising a first spunbond nonwoven fabric, a meltblown nonwoven fabric adjacent to the first spunbond nonwoven fabric, a second spunbond nonwoven fabric adjacent to the meltblown nonwoven fabric, and a third spunbond nonwoven fabric adjacent to the second spunbond nonwoven fabric.

8. 8. The sound absorbing wall structure according to claim 7, wherein at least one selected from the group consisting of the first spunbond nonwoven fabric, the second spunbond nonwoven fabric, and the third spunbond nonwoven fabric contains fibers having an average fiber diameter in the range of 25 to 50 μm.

9. 8. The sound absorbing wall structure of claim 7, wherein the meltblown nonwoven fabric comprises fibers having an average fiber diameter in the range of 0.5 to 5 μm.

10. 8. The sound absorbing wall structure according to claim 7, wherein at least one selected from the group consisting of the first spunbond nonwoven fabric, the second spunbond nonwoven fabric, and the third spunbond nonwoven fabric comprises hollow fibers.

11. 2. The sound-absorbing wall structure according to claim 1, wherein the amount of sagging of the padding is 75 mm or less when measured by the following test method. The filling, which is 500 mm wide, 1000 mm long, and 50 mm thick, is placed on the top of a desk that is 500 mm or wider and 1000 mm or wider, placed on a horizontal floor, so that the length of the filling is parallel to the length of the desk, the filling is contained in the width direction of the desk, and the filling extends 600 mm from one side of the desk in the length direction, and the distance from the floor to the desk top and the distance from the floor to the bottom surface of the tip of the filling sample are measured. Sagging amount = Distance from floor to desk top - Distance from floor to bottom of tip of filling sample

12. In the sound-absorbing wall structure according to claim 1, the carbon dioxide emission of the skin and the padding is 8.0 kg / m, calculated in accordance with the calculation method of the 3R basic unit reported by the Recycling Society Promotion Office, Planning Division, Waste and Recycling Department, Ministry of the Environment. ２ The sound-absorbing wall structure is as follows.

13. 13. The sound absorbing wall structure according to claim 1, wherein a clearance between the sound absorbing panel and the sound absorbing wall is 5 to 200 mm.

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