JP7634850B2 - Sound-absorbing material, sound-absorbing panel using same, and method for manufacturing sound-absorbing material - Google Patents

Description

The present invention relates to a sound-absorbing material, a sound-absorbing panel using the same, and a method for manufacturing the sound-absorbing material.

Conventionally, there has been known a sound-absorbing material made of a laminated nonwoven fabric, in which a first nonwoven fabric made of polyethylene terephthalate resin fibers and having a specific range of density, thickness and breathability is used as a surface layer (skin material), and a second nonwoven fabric made of polyethylene terephthalate resin short fibers and having a specific range of basis weight and thickness is used as a base layer (filling) (see, for example, Patent Document 1).

According to the sound-absorbing material described in Patent Document 1, the first nonwoven fabric and the second nonwoven fabric are laminated together to provide an excellent sound absorption rate in the low frequency range of 800 to 1250 Hz.

International Publication No. 2016/143857

However, sound-absorbing materials made of short fibers of polyethylene terephthalate resin, such as the sound-absorbing material described in Patent Document 1, have the disadvantage that their sound absorption rate decreases in environments with a lot of moisture.

Therefore, the present invention aims to provide a sound-absorbing material whose sound absorption rate is less likely to decrease even in a humid environment.

In order to achieve this object, the sound-absorbing material of the present invention comprises a filling containing fibers made of at least a polyester-based resin and a skin material containing the filling, and the filling is contained in the skin material by an end of the skin material fused by an ultrasonic sealing method , and the skin material is made of a nonwoven fabric containing fibers made of a polypropylene-based resin, and is provided with a first spunbond nonwoven fabric, a meltblown nonwoven fabric located on the first spunbond nonwoven fabric, a second spunbond nonwoven fabric located on the meltblown nonwoven fabric, and a third spunbond nonwoven fabric located on the second spunbond nonwoven fabric, and the third spunbond nonwoven fabric has an average fiber diameter in the range of 30 to 50 μm and a basis weight in the range of 70 to 150 g/ ^m2 .

Since fibers made of polypropylene resin are hydrophobic, the sound-absorbing material of the present invention does not come into contact with water because the filling is enclosed in the skin material, and the sound absorption rate is less likely to decrease even in a humid environment.

The sound-absorbing material of the present invention has an excellent sound absorption coefficient in the low frequency range of 800 to 1250 Hz because the padding contains fibers made of at least polyester-based resin, but it is preferable that it further contains fibers made of polypropylene-based resin.

In the sound-absorbing material of the present invention, the skin preferably has a water pressure resistance in the range of 200 to 2000 mmH ₂ O to prevent the filling from coming into contact with water. If the water pressure resistance of the skin is less than 200 mmH ₂ O, it may not be possible to prevent the filling from coming into contact with water, and even if it exceeds 2000 mmH ₂ O, it is not easy to obtain any greater effect.

However, when the sound-absorbing material of the present invention is used outdoors, it may be worn down by the impact of solid objects such as hailstones, sleet, or pebbles, shortening its lifespan. Therefore, it is desirable for the skin material to have abrasion resistance (shot blast resistance) against the impact of solid objects as well as water pressure resistance.

In the sound absorbing material of the present invention, the skin material includes a first spunbond nonwoven fabric, a meltblown nonwoven fabric located on the first spunbond nonwoven fabric, and a second spunbond nonwoven fabric located on the meltblown nonwoven fabric in order to provide both the water pressure resistance and the shot blast resistance in the above range . Generally, the average fiber diameter of the fibers contained in the meltblown nonwoven fabric is smaller than the average fiber diameter of the fibers contained in the spunbond nonwoven fabric, so that the meltblown nonwoven fabric provides the water pressure resistance in the above range, while the first or second spunbond nonwoven fabric located on the outer layer of the meltblown nonwoven fabric provides the shot blast resistance and protects the meltblown nonwoven fabric. In this case, the meltblown nonwoven fabric preferably contains fibers having an average fiber diameter in the range of 0.5 to 5 μm in order to obtain the water pressure resistance in the above range, and the first or second spunbond nonwoven fabric preferably contains fibers having an average fiber diameter in the range of 25 to 50 μm in order to obtain the shot blast resistance.

The sound-absorbing panel of the present invention is characterized by comprising any one of the sound-absorbing materials described above and a frame for housing the sound-absorbing material.

The method for producing a sound-absorbing material of the present invention is characterized in that it includes a fusion step of wrapping a filling containing fibers made of at least a polyester-based resin with a skin material which is a nonwoven fabric containing fibers made of a polypropylene- based resin, fusing edges of the skin material by an ultrasonic sealing method, and enclosing the filling in the skin material by the ultrasonically fused edges of the skin material .

1 is an explanatory cross-sectional view showing the configuration of a first embodiment of a sound-absorbing material of the present invention. FIG. 4 is an explanatory cross-sectional view showing the configuration of a second embodiment of the sound-absorbing material of the present invention. FIG. 2 is an explanatory cross-sectional view showing one example of the configuration of the sound-absorbing panel of the present invention.

Next, an embodiment of the present invention will be described in more detail with reference to the attached drawings.

As shown in Fig. 1, the first embodiment of the sound-absorbing material 1 of this embodiment is composed of, for example, at least a filling 2 containing fibers made of polyester-based resin, 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 portions 4 on three sides of its periphery. As a result, the filling 2 is surrounded by the folded portions of the skin material 3 and the seal portions 4, and is contained in the skin material 3.

In addition, the filling 2 only needs to be enclosed by the skin material 3, and the configuration for enclosing the filling 2 in the skin material 3 is not limited to the configuration shown in Figure 1.

For example, as in the second embodiment of the sound-absorbing material 1 of this embodiment shown in Figure 2, it may be configured to be composed of 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 the periphery that surrounds the filling 2.

The basis weight of the sound-absorbing material 1 is preferably in the range of 500 to 3000 g/m2, more preferably in the range of 1000 to 2500 g/m2, and most preferably in the range of 1300 to 2200 g/ ^m2 , from the viewpoint of further improving the sound absorption coefficient mainly in the range of 100 to 2000 ^Hz , from the viewpoint of preventing a decrease in workability due to an increase in the weight of the sound-absorbing material, and further from the viewpoint of preventing the increase in weight from making it difficult to ensure the strength of ^{the structure} supporting the sound-absorbing material.

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 viewpoint of further improving the sound absorption rate in the low frequency range, particularly in the range of 100 to 1000 Hz, and from the viewpoint of ensuring efficient space when installing it in a structure, etc.

The padding 2 may be made of only fibers made of polyester resin such as polyethylene terephthalate resin, or may further contain fibers made of polypropylene resin. By including fibers made of polyethylene terephthalate resin and fibers made of polypropylene resin, the padding 2 can have the effect of more easily maintaining an appropriate balance between bulkiness (ensuring sound absorption rate) and hydrophobicity.

As the filling 2, for example, a nonwoven fabric molding containing short fibers of the polyester (polyethylene terephthalate) resin and short fibers of the polypropylene resin can be used.

The basis weight of the filling 2 is preferably in the range of 400 to 2900 g/m2, more preferably in the range of 900 to 2400 g/m2, and most preferably in the range of 1200 to 2100 g/ ^m2 , from the viewpoint of further improving the sound absorption coefficient mainly in the range of 100 to 2000 Hz, from the viewpoint of preventing a decrease in workability due to an increase in the weight of the sound-absorbing material, ^and further from the viewpoint of preventing the strength of the structure supporting the sound-absorbing material from being difficult to ensure due to an increase in ^weight .

The polyester (polyethylene terephthalate) resin short fibers and the polypropylene resin short fibers may be manufactured by a known melt spinning method, or may be purchased from a commercial source. The polyester (polyethylene terephthalate) resin short fibers 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 short fibers 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.

From the viewpoint of further improving the sound absorption coefficient, the ratio of polyester-based resin short fibers to polypropylene-based resin short fibers in the nonwoven fabric molding is preferably, by mass, polyester-based resin short fibers:polypropylene-based resin short 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.

The nonwoven fabric body can be obtained, for example, by mixing 1 to 95% by mass, e.g. 60% by mass, of the polypropylene-based resin staple fibers with 99 to 5% by mass, e.g. 40% by mass, of polyester (polyethylene terephthalate) binder staple fibers, forming a web using a fiber spreader and a carding machine, laminating the resulting web in multiple layers using a cross-layer machine, and processing it with a hot air processing machine set to a predetermined gap distance to fuse the polyester (polyethylene terephthalate) binder staple fibers and the polypropylene-based resin staple fibers.

The polyethylene terephthalate resin may be a copolymer of a polyhydric alcohol such as ethylene glycol and a dibasic acid such as terephthalic acid. Examples of such polyethylene terephthalate resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyethylene isophthalate (PEI), polybutylene isophthalate (PBI), polyhexamethylene terephthalate (PHT), polyhexamethylene isophthalate (PHI), and polyhexamethylene naphthalate (PHN).

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-olefins 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.

The polyester (polyethylene terephthalate) binder staple fiber may, for example, have a polyethylene terephthalate core and a binder component in the sheath. Examples of the binder component include copolymer polyesters made of terephthalic acid or its ester-forming derivatives, isophthalic acid or its ester-forming derivatives, lower alcohols, and polyalkylene glycols or their monoethers.

The polyester-based resin staple fibers and polypropylene-based resin staple fibers in the nonwoven fabric body may include composite fibers, hollow fibers, irregular fibers, crimped fibers, split fibers, etc., within the scope of the invention. They may also include heat stabilizers, ultraviolet absorbers, weather stabilizers, flame retardants, water repellents, oils, antistatic agents, colorants, inorganic substances, etc.

The skin material 3 is made of a nonwoven fabric containing fibers made of a polypropylene-based resin. From the viewpoint of further preventing contact between the filling 2 and water, the skin material 3 preferably has a water pressure resistance in the range of 200 to 2000 _{mmH 2 O} , more preferably has a water pressure resistance in the range of 200 to 500 mmH ₂ O, further preferably has a water pressure resistance in the range of 250 to 450 mmH ₂ O, and most preferably has a water pressure resistance in the range of 280 to 400 mmH 2 O. The water pressure resistance of the skin material 3 can be further increased by, for example, reducing the average fiber diameter of the fibers constituting the skin material 3, increasing the density, and increasing the basis weight.

The weight of the skin material 3 is preferably in the range of 50 to 200 g/m2, and more preferably in the range of 70 to 150 g/m2, from the viewpoints of further improving the water pressure resistance and further preventing contact between the filling 2 and water, maintaining strength such as shot blast resistance, preventing a situation in which the weight is too high and sound waves are less likely to be transmitted to the filling ² side, and preventing a situation in which the weight is too high and workability of ^ultrasonic sealing and the like is reduced.

The air permeability of the skin material 3 is preferably in the range of 5 to 200 cm 3 /cm ² /sec, more preferably in the range of 7 to 150 cm 3 /cm ² /sec, and most preferably in the range of 10 to 50 ^{cm 3 /} cm ² /sec, from the viewpoints of further improving the water pressure resistance and further preventing contact between the padding and water, and of adequately transmitting sound waves to ^{the padding} side to maintain a good sound absorption coefficient.

The thickness of the skin material 3 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 thus preventing contact between the filling 2 and water, maintaining strength such as shot blast resistance, preventing the material from being too thick and thus making it difficult for sound waves to be transmitted to the filling side, and preventing the material from being too thick and thus reducing the ease of use of ultrasonic sealing, etc.

The average fiber diameter of the fibers located near the surface of the skin material 3 (hereinafter sometimes referred to as the surface fiber diameter) is preferably in the range of 20 to 100 μm, and more preferably in the range of 30 to 50 μm, from the viewpoint of further improving shot blast resistance and controlling the breathability within an appropriate range.

The polypropylene-based resin used in the nonwoven fabric constituting the skin material 3 may be a homopolymer of propylene, similar to the polypropylene-based resin used in the filling 2, or may be a copolymer of propylene and other α-olefins copolymerizable with propylene. As the α-olefin, one or more of the same α-olefins as in the polypropylene-based resin used in the filling 2 can be used.

The fibers constituting the skin material 3 may contain heat stabilizers, ultraviolet absorbers, weather stabilizers, flame retardants, water repellents, oils, antistatic agents, colorants, inorganic substances, etc., within the scope of the invention.

The polypropylene resin used in the nonwoven fabric constituting the skin material 3 may have an MFR (melt flow rate) in the range of, for example, 10 to 100 g/min. In the sound-absorbing material 1 of this embodiment, 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.

The inventors have found that, while the smaller (thinner) the average fiber diameter of the fibers contained in a nonwoven fabric, the denser it is and the better its water pressure resistance, from the standpoint of abrasion resistance (shot blast resistance) against the impact of solid objects such as hail, sleet, or pebbles, it is desirable for the average fiber diameter of the fibers contained to be larger (thicker). In addition, the average fiber diameter of the fibers contained in a spunbond nonwoven fabric is larger than the average fiber diameter of the fibers contained in a meltblown nonwoven fabric, and the average fiber diameter of the fibers contained in a meltblown nonwoven fabric is smaller than the average fiber diameter of the fibers contained in a spunbond nonwoven fabric.

Therefore, the skin material 3 has at least a four-layer structure (hereinafter, the four-layer structure may be referred to as an SSMS structure or SMSS structure) including a first spunbond nonwoven fabric containing fibers made of a polypropylene-based resin having an average fiber diameter in the range of 25 to 50 μm, a meltblown nonwoven fabric containing fibers made of a polypropylene-based resin having an average fiber diameter in the range of 0.5 to 5 μm located on the first spunbond nonwoven fabric , a second spunbond nonwoven fabric containing fibers made of a polypropylene-based resin having an average fiber diameter in the range of 25 to 50 μm located on the meltblown nonwoven fabric, and a third spunbond nonwoven fabric having an average fiber diameter in the range of 30 to 50 μm and a basis weight in the range of 70 to 150 g / m ² located on the second spunbond nonwoven fabric, and the third spunbond nonwoven fabric has a fiber diameter in the range of 30 to 50 μm and a basis weight in the range of 70 to 150 g / m 2. The third spunbond nonwoven fabric can provide better shot blast resistance.

When the skin material 3 has the above-mentioned structure , the meltblown nonwoven fabric forming the inner layer has a small average fiber diameter and is dense, thereby ensuring the above-mentioned range of water pressure resistance. On the other hand, the meltblown nonwoven fabric contains fibers with a small average fiber diameter, so it is prone to fluffing and may have poor shot blast resistance. Therefore, 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.

The spunbond nonwoven fabric can be manufactured using a known spunbond nonwoven fabric molding machine. More specifically, the spunbond nonwoven fabric can be manufactured, for example, by melting the raw material polypropylene resin using an extruder, discharging the molten composition from multiple spinnerets, cooling and stretching the fibrous resin as necessary, depositing it on a collection surface, and subjecting it to a heating and pressurizing treatment using an embossing roll.

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

The sealed portion 4 can be formed by ultrasonic sealing. The sealed portion 4 may be formed continuously or discontinuously on the peripheral portion of the skin material 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.

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 mmH ₂ O or more, more preferably 150 mmH ₂ O or more, even more preferably 200 mmH ₂ O or more, particularly preferably 250 mmH ₂ O or more, and most preferably 300 mmH ₂ O 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 mmH ₂ O or less, 1000 mmH ₂ O or less, or 500 mmH ₂ O or less.

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

The width of the seal portion 4 is not particularly limited as long as the effects of the present invention can be achieved, but it is preferable that the width is in the range of 0.1 to 5.0 mm from the viewpoint of further improving the water pressure resistance of the seal portion while suppressing tearing. The width of the seal portion 4 can be, for example, 0.3 mm.

Next, referring to Figure 3, the sound-absorbing panel of this embodiment will be described.

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 protective 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.

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.

It is preferable that the protective panel 15 protects the sound-absorbing material 1 from solid objects such as hail, sleet, or pebbles while facilitating the penetration of sound waves. For this reason, in this embodiment, a punched plate with many through holes 15a arranged on the surface is preferably used as the protective panel 15, but it 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%.

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 the intrusion of sound waves, weather, moisture, etc., and can be made of metal or resin. As for metal, lightweight metals such as aluminum and stainless steel are preferably used.

Next, we will explain the manufacturing method of the sound-absorbing material 1 of this embodiment shown in Figure 1 or Figure 2.

The sound-absorbing material 1 can be manufactured, for example, by a manufacturing method including a fusion process in which a filling 2 containing fibers made of at least polyester-based resin is wrapped in a skin material 3 which is a nonwoven fabric containing fibers made of polypropylene-based resin, and the ends of the skin material 3 are fused together.

The ends are fused using an ultrasonic sealing method .

The output of the ultrasonic sealing device in the ultrasonic sealing method 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. The pressure in the 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. 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.

Next, examples and comparative examples of the present invention are shown.

In the following examples and comparative examples, the physical properties and performance of the sound-absorbing material were measured or evaluated as follows.

[Weight (g/m ² )]
Five samples of 10 cm square were taken from the sound-absorbing material so as not to include the side peripheral surface. The weight of each sample was then measured, and the total weight was divided by the total area to calculate the basis weight (g/m ² ).

[Thickness (mm)]
For the five samples used in calculating the basis weight, the thickness of the center of each of the four sides of each sample was measured with a steel ruler, and the average value was taken as the thickness (mm).

[Water pressure resistance of surface material]
The skin material used for the sound-absorbing material (if there was no skin material, five 15 cm square samples were taken from the surface region sliced to a thickness of 5 mm or less) and the water pressure resistance was measured according to JIS L 1096 (2010) Method A (low water pressure method), and the average value was taken as the water pressure resistance of the skin material.

[Water pressure resistance of seal part]
When the skin material was taken from the sound absorbing material, the seal portion was taken so as to be included in the center of the 15 cm square sample, and the water pressure resistance of the seal portion was determined to be the same as the water pressure resistance of the skin material.

[Air permeability ( ^cm3 / ^cm2 /sec)]
Five 15 cm square samples were taken from the skin material used for the sound-absorbing material, with the same water pressure resistance as the skin material, and the air permeability was measured using a Frazier air permeability tester in accordance with JIS L 1096 (2010), and the average value was taken as the air permeability ( ^cm3 / ^cm2 /sec).

[Shot blast resistance]
A 25 cm square sound-absorbing material was used as a sample, and a shot blast test was carried out under conditions of S30 (steel ball), a spray nozzle diameter of 5 mm, a distance from the nozzle tip to the top surface of the sample of 150 mm, and a spray air pressure of 0.1 MPa, and after 4 seconds of spraying, if the skin material was torn it was marked with an X, if it was not torn it was marked with an O, and if it was not torn but damage was observed over an area of more than half the thickness of the skin material it was marked with a △.

[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 piece 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.

[Surface fiber diameter]
The fiber diameters (μm) of 30 constituent fibers of a sample piece taken from a spunbonded nonwoven fabric were measured at a magnification of 50x or 100x using a scanning electron microscope (manufactured by Hitachi, Ltd., model name: SU3500), and the average value was taken as the surface fiber diameter. Portions in which the fibers were fused together and the interface was unclear, making it impossible to identify the diameter of each fiber, were excluded. Note that the cross section of the skin material was observed with a scanning electron microscope , and when no fusion was observed in the non-embossed portion, the average fiber diameter was taken as the surface fiber diameter.

[Fusion between fibers in non-embossed portion]
The surface of the spunbond nonwoven fabric on the outermost surface of the skin material was observed using a scanning electron microscope (manufactured by Hitachi, Ltd., model name: SU3500), and if the fusion shape was different from the embossed shape, it was determined that there was fusion between the fibers in the non-embossed portion. If the fusion shape was the same as the embossed shape, it was determined that there was no fusion between the fibers in the non-embossed portion.

[Sound absorption coefficient]
In accordance with 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. Note that the sound absorption coefficient for the 1/3 octave band center frequency of 50 to 1250 Hz is the measurement result for the thick tube, and the sound absorption coefficient for the 1600 to 2000 Hz is the measurement result for the thin tube.

[Water immersion test]
A 10 cm square sound absorbing material was used as a sample, and the sample was gently floated on the surface of 1 liter of distilled water contained in a 2 liter beaker, and the state was observed after 1 hour. If there was no change from immediately after floating, it was marked as no water infiltration (○), and if the sound absorbing material sank below the water surface compared to immediately after floating, it was marked as water infiltration (×). In addition, if the skin material was provided on only one side of the sound absorbing material, it was floated on the surface of the distilled water with the side with the skin material as the upper surface. In addition, after the water immersion test, the sound absorption coefficient was measured, and the change rate (%) of the sound absorption coefficient after the water immersion test was calculated using the following formula (1).

Rate of change in sound absorption coefficient after water immersion test (%) = sound absorption coefficient after water immersion test / sound absorption coefficient before water immersion test ... (1)
Example 1
In this example, the sound absorbing material was obtained as follows.

<Preparation of Skin Material>
A propylene homopolymer having a melt flow rate (MFR) of 60 g/10 min was used, and melt spinning was carried out at 230°C by a conventional spunbonding method using a spunbond nonwoven fabric molding machine having a spinneret with a diameter of 0.6 mm. The fibers obtained by spinning were deposited on a collection surface to obtain a first spunbond nonwoven fabric A-1 having an average fiber diameter of 16 μm and a basis weight of 10 g/ ^m2 .

Next, a propylene homopolymer having an MFR of 400 g/10 min was melted at 280° C. using an extruder, and the resulting molten material was extruded from a spinneret and heated air at 280° C. was blown onto the first spunbond nonwoven fabric A-1 by a conventional meltblown method to deposit fibers having an average fiber diameter of 3 μm, thereby forming a meltblown nonwoven fabric B-1 having a basis weight of 5 g/ ^m2 .

Next, fibers were deposited on the meltblown nonwoven fabric B-1 in the same manner as the first spunbond nonwoven fabric A-1 to form a second spunbond nonwoven fabric A-2 having an average fiber diameter of 16 μm and a basis weight of 10 g/m ² .

Next, the laminate of the first spunbond nonwoven fabric A-1, the meltblown nonwoven fabric B-1, and the first spunbond nonwoven fabric A-2 was integrated by a hot embossing roll with an imprint area ratio of 18% set at a temperature of 145°C for the embossing roll and 150°C for the mirror roll, to obtain a three-layer structure (hereinafter referred to as 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 SMS structure nonwoven fabric was 25 g/ ^m2 .

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 using a spunbond 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 nonwoven fabric to form a third spunbond nonwoven fabric C having an average fiber diameter of 35 μm and a basis weight of 100 g/m ^2. Next, the laminate of the SMS nonwoven fabric and the third spunbond nonwoven fabric C was integrated using a hot embossing roll (embossed pattern 0.9 mm square) with an imprint area ratio of 18% and a temperature set to an embossing roll of 155° C. and a mirror roll of 160° C., to obtain a skin material consisting of a four-layer structure (hereinafter referred to as SSMS structure) nonwoven fabric in which the third spunbond nonwoven fabric C was laminated on the SMS nonwoven fabric. The structure of the skin material is sometimes referred to as PP-SSMS.

<Preparation of filling>
60 parts by mass of polypropylene staple fibers (manufactured by Ube Exsymo Co., Ltd., product name: UC Fiber, average fiber diameter 21 μm, average fiber length 51 mm) and 40 parts by mass of polyethylene terephthalate (polyester) binder staple fibers (manufactured by Unitika Ltd., product name: Melty 4080, average fiber diameter 14 μm, average fiber length 51 mm) were mixed and formed into a web using a fiber spreader and 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 filling consisting of a sheet-like nonwoven fabric molding containing polypropylene staple fibers and polyethylene terephthalate staple fibers and having a thickness of about 50 mm.

<Preparation of sound absorbing material>
Next, the filling was cut to 250 mm (length) x 250 mm (width) x 49 mm (thickness). Next, the skin material was placed on both sides of the cut filling with the third spunbond nonwoven fabric C on the outermost surface, and the peripheral portion of the skin material around the filling was fused with an ultrasonic sealer (manufactured by Seidensha Denshi Kogyo Co., Ltd., product name: JII430SA) under conditions of output of 2.0 V, pressure of 0.3 MPa, and speed of 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 filling is enclosed in the skin material. The excess portion on the outer periphery of the seal portion was cut off and removed.

Next, the physical properties and performance of the sound-absorbing material obtained in this example were measured or evaluated as described above. The physical properties are shown in Table 1, the sound absorption coefficient among the performances is shown in Table 2, and the rate of change in the sound absorption coefficient after the water immersion test is shown in Table 3.

Example 2
In this example, a sound-absorbing material was obtained in exactly the same manner as in Example 1 , except that the average fiber diameter of the third spunbond nonwoven fabric C-1 was set to 40 μm by adjusting the amount of air during melt spinning. Next, the physical properties and performance of the sound-absorbing material obtained in this example were measured or evaluated as described above. The physical properties are shown in Table 1, the sound absorption coefficient among the performances is shown in Table 2, and the rate of change in the sound absorption coefficient after the water immersion test is shown in Table 3.

Example 3
In this example, a sound-absorbing material was obtained in exactly the same manner as in Example 1, except that a propylene homopolymer with an MFR of 900 g/10 min was used as the resin for the meltblown nonwoven fabric. Next, the physical properties and performance of the sound-absorbing material obtained in this example were measured or evaluated as described above. The results are shown in Table 1.

Example 4
In this example, a sound-absorbing material was obtained in exactly the same manner as in Example 1, except that when preparing the filling, the number of layers in the cross-layer machine was adjusted, and the gap distance of the hot air treatment machine was set to 25 mm to obtain a filling having a thickness of 25 mm. Next, the physical properties and performance of the sound-absorbing material obtained in this example were measured or evaluated as described above. The physical properties are shown in Table 1, the sound absorption coefficient among the performances is shown in Table 2, and the rate of change in the sound absorption coefficient after the water immersion test is shown in Table 3.

Comparative Example 1
In this comparative example, a sound absorbing material with a skin on one side was obtained by laminating a skin material made of polyester (polyethylene terephthalate) nonwoven fabric ( made by Toyobo Co., Ltd., product name: Heim, fiber diameter 15 μm, basis weight 120 g/m 2 ) using spray glue (made by 3M, product number: 77) to only one surface of a filling made of a sheet-like nonwoven fabric molding containing 60 parts by mass of polyethylene terephthalate (polyester) staple fibers (manufactured by Teijin Frontier Co., Ltd., product name: Tetoron, average fiber diameter 30 μm, average fiber length 51 ^mm ) and 40 parts by mass of the same polyethylene terephthalate (polyester) binder staple fibers as in Example 1. The configuration of the skin material made of a single layer of spunbond nonwoven fabric made of polyethylene terephthalate fibers is sometimes called PET-SB.

Next, the physical properties and performance of the sound-absorbing material obtained in this comparative example were measured or evaluated as described above. The physical properties are shown in Table 1, the sound absorption coefficient among the performances is shown in Table 2, and the rate of change in the sound absorption coefficient after the water immersion test is shown in Table 3.

Comparative Example 2
In this comparative example, a skin material made of a commercially available polyester (polyethylene terephthalate) nonwoven fabric (manufactured by Unitika Ltd., product name: polyester taffeta, water-repellent finish, fiber diameter 23 μm, basis weight 100 g/ ^m2 ) was laminated on both the front and back sides of the same padding as in Comparative Example 1, and a seal was formed by sewing to obtain a sound-absorbing material.

Next, the physical properties and performance of the sound-absorbing material obtained in this comparative example were measured or evaluated as described above. The physical properties are shown in Table 1, the sound absorption coefficient among the performances is shown in Table 2, and the rate of change in the sound absorption coefficient after the water immersion test is shown in Table 3.

Comparative Example 3
In this comparative example, a sound-absorbing material was obtained in the same manner as in Comparative Example ² , except that a commercially available polyethylene terephthalate (polyester) nonwoven fabric (manufactured by Unitika Ltd., product name: polyester taffeta, water-repellent finish) with a fiber diameter of 20 μm and a basis weight of 100 g/m2 was used as the skin material.

Next, the physical properties and performance of the sound-absorbing material obtained in this comparative example were measured or evaluated as described above. The physical properties are shown in Table 1, the sound absorption coefficient among the performances is shown in Table 2, and the rate of change in the sound absorption coefficient after the water immersion test is shown in Table 3.

It is clear from Tables 1 to 3 that the sound absorbing materials of Examples 1 to 4 , in which the filling containing at least polyester-based resin fibers is enclosed in a skin material made of nonwoven fabric containing polypropylene-based resin fibers, do not lose their sound absorption coefficient even in a humid environment. In contrast, it is clear that the sound absorbing materials of Comparative Examples 1 to 3, in which the skin material is made of nonwoven fabric containing polyester-based resin fibers, lose their sound absorption coefficient in a humid environment.

1...sound-absorbing material, 2...padding, 3...skin material, 4...sealing portion, 11...sound-absorbing panel, 12...shielding plate, 13...side wall, 14...frame, 15...protective panel, 16...support portion.

Claims (7)

A sound absorbing material comprising a filling material containing at least a fiber made of a polyester resin and a skin material containing the filling material, the filling material being contained in the skin material by an end of the skin material fused by an ultrasonic sealing method ,
The skin material is made of a nonwoven fabric containing fibers made of a polypropylene-based resin,
A first spunbond nonwoven fabric, a meltblown nonwoven fabric located on the first spunbond nonwoven fabric, a second spunbond nonwoven fabric located on the meltblown nonwoven fabric, and a third spunbond nonwoven fabric located on the second spunbond nonwoven fabric,
The third spunbond nonwoven fabric is a sound-absorbing material characterized in that the average fiber diameter is in the range of 30 to 50 μm and the basis weight is in the range of 70 to 150 g/ ^m2 . The sound-absorbing material according to claim 1, characterized in that the padding contains fibers made of polypropylene-based resin. 3. The sound absorbing material according to claim 1, wherein the surface material has a water pressure resistance in the range of 200 to 2000 _mmH2O . The sound absorbing material according to any one of claims 1 to 3, characterized in that the first or second spunbond nonwoven fabric contains fibers with an average fiber diameter in the range of 25 to 50 μm. The sound-absorbing material according to any one of claims 1 to 4, characterized in that the meltblown nonwoven fabric contains fibers with an average fiber diameter in the range of 0.5 to 5 μm. A sound-absorbing panel comprising the sound-absorbing material according to any one of claims 1 to 5 and a frame that houses the sound-absorbing material. The method includes a fusion step of wrapping a filling material containing at least a fiber made of a polyester resin with a skin material which is a nonwoven fabric containing a fiber made of a polypropylene resin, fusing the ends of the skin material by an ultrasonic sealing method , and enclosing the filling material in the skin material by the ends of the skin material which have been ultrasonically fused ,
The skin material is made of a nonwoven fabric containing fibers made of a polypropylene-based resin,
A first spunbond nonwoven fabric, a meltblown nonwoven fabric located on the first spunbond nonwoven fabric, a second spunbond nonwoven fabric located on the meltblown nonwoven fabric, and a third spunbond nonwoven fabric located on the second spunbond nonwoven fabric,
The third spunbond nonwoven fabric has an average fiber diameter in the range of 30 to 50 μm and a basis weight in the range of 70 to 150 g/ ^m2 .

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