JP4285683B2 - Sound absorbing material and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sound-absorbing material comprising a sheet-like assembly in which organic fibers are entangled with each other, and a method for producing the same. In particular, the present invention relates to a sound absorbing material characterized in that the organic fiber is a short fiber partially fibrillated and a method for producing the same.
[0002]
[Prior art]
With increasing interest in noise problems in recent years, various fiber sound absorbing materials have been used in buildings and the like as noise prevention measures. Such a sound absorption phenomenon by the fiber sound-absorbing material is described as a complex intertwining of absorption due to the shape of a continuous hole through which gas passes and absorption of vibration by the fiber itself. In general, it is known that in the case of a fiber sound-absorbing material, if the fiber type is the same, the smaller the diameter, the better the sound-absorbing property in the low-frequency region. A method using fibers has been proposed.
[0003]
For example, Japanese Patent Application Laid-Open No. 10-251951 (Patent Document 1) describes a sound-absorbing sheet made of PVA-based fibril fibers containing 50% by weight or more of a polyvinyl alcohol polymer and having an average diameter of 0.05 to 5 μm. Has been. This fibril fiber is preferably obtained by splitting a sea-island phase-separated structure fiber composed of PVA and a polymer incompatible therewith, and the fibril fiber and other organic fibers are mixed. It is also described that a sound absorbing sheet can be constructed. By adopting such a configuration, it is said that a material that is lightweight and exhibits good sound absorption performance for sound in a low frequency region can be provided.
[0004]
Japanese Patent Laid-Open No. 10-245452 (Patent Document 2) describes a sound absorbing material in which a mixture of an inorganic fibrous material and fibrillated organic fibers forms a porous molded body. This sound-absorbing material has high sound-absorbing performance for medium and low-frequency sounds, and there is no loss of fibers due to vibration. The fibrillated organic fiber used here is an organic fiber fibril having an ultrafine diameter of several μm or less, or an organic fiber having ultrafine diameter whisker projections of several μm or less on the surface of the fiber. Has been. It is said that by mixing inorganic fibers with this, it becomes nonflammable and the bulk density can be increased to improve the sound absorption coefficient.
[0005]
[Patent Document 1]
JP-A-10-251951 (Claims, pages 2-3)
[Patent Document 2]
Japanese Patent Laid-Open No. 10-245452 (Claims, pages 2 to 3)
[0006]
[Problems to be solved by the invention]
It is known that the sound-absorbing material needs to have a certain degree of air permeability. However, when a fiber assembly is produced using only ultrafine fibers, for example, if it is a cellulosic fiber, it will be paper-like, but the air permeability is low. Therefore, even if a thick assembly is produced, reflection near the surface is increased and air vibrations are not transmitted to the inside. In addition, the aggregate composed of only ultrafine fibers is soft and requires processing such as pasting with other materials in order to stabilize the form.
[0007]
The thickness of the sound-absorbing sheet described in the examples of JP-A-10-251951 is 0.5 to 0.6 mm, and the air permeability is not considered at all because the thickness is small. In addition, the sound-absorbing sheet is manufactured by splitting PVA and other composite fibers, and as a result of mixing a plurality of materials, it is difficult to recycle. In addition, since the sound absorbing material described in JP-A-10-254442 contains a large amount of inorganic fibrous material, it is difficult to separate organic and inorganic materials when it is disposed of, and recycling is also required. Hateful.
[0008]
The present invention has been made to solve the above problems, and has a sound absorbing material excellent in air permeability and shape retention while having excellent sound absorbing properties in a wide frequency range, particularly in a low frequency range, and a method for producing the same. The purpose is to provide. It is also an object of the present invention to make it possible to produce a sound-absorbing material from waste fiber products and to use the used sound-absorbing material again as a new material for the sound-absorbing material.
[0009]
[Means for Solving the Problems]
The above-mentioned problem is a sound-absorbing material composed of a sheet-like assembly in which organic fibers are entangled with each other, and the organic fibers are partially fibrillated and have a diameter of 0.1 to 4 μm and a length of 10 μm or more. And a short fiber having a diameter of 5 to 100 μm and a non-fibrillated large-diameter portion, which consists essentially of a single material organic fiber , and the thickness of the sheet-like aggregate is 5 This is solved by providing a sound-absorbing material characterized in that the sheet-like aggregate has an air permeability of 1 to 100 cm ³ / cm ² · sec. By using the partially fibrillated short fiber, the sound absorption in the low frequency region is improved by the fibrillated portion, and the air permeability and the shape retention are ensured by the non-fibrillated portion.
[0010]
At this time, the length of the short fiber is preferably 0.2 to 10 mm .
[0011]
The above-mentioned problem is a method for producing a sound-absorbing material comprising a sheet-like assembly in which organic fibers are entangled with each other, wherein the organic fibers are partially fibrillated and have a diameter of 0.1 to 4 μm and a length. It is a short fiber having a portion of ultrafine fibers of 10 μm or more and a non-fibrillated large diameter portion having a diameter of 5 to 100 μm, the organic fiber is a main constituent, and the thickness of the sheet-like aggregate is Short fibers that are 5 to 50 mm, and the air permeability of the sheet-like aggregate is 1 to 100 cm ³ / cm ² · sec, and are physically fibrillated by giving a physical impact to a discarded fiber product The problem can also be solved by providing a method for producing a sound-absorbing material , wherein the short fibers are entangled with each other to form a sheet-like aggregate. At this time, a method is preferred in which the short fibers are stirred and dispersed in a liquid and then made into paper to form a sheet-like aggregate.
[0012]
The above-mentioned problem is a method for producing a sound-absorbing material comprising a sheet-like assembly in which organic fibers are entangled with each other, wherein the organic fibers are partially fibrillated and have a diameter of 0.1 to 4 μm and a length. It is a short fiber having a portion of ultrafine fibers of 10 μm or more and a non-fibrillated large diameter portion having a diameter of 5 to 100 μm, the organic fiber is a main constituent, and the thickness of the sheet-like aggregate is a 5 to 50 mm, and the a air permeability 1~100cm ³ / ^cm 2 · sec for the sheet-like aggregate, after opening the sound absorbing material, that to form a sheet-like aggregates are entangled again The problem can also be solved by providing a method for manufacturing a sound-absorbing material. These production methods are preferable from the viewpoint of resource recycling.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The sound-absorbing material of the present invention is a sound-absorbing material comprising a sheet-like aggregate in which organic fibers are entangled with each other, and the organic fibers are short fibers that are partially fibrillated.
[0014]
The organic fiber used as a raw material here is not particularly limited as long as it is a fiber that can be partially fibrillated to generate ultrafine fibers. Since fibrillation is easy, cellulosic fibers such as cotton, hemp, polynosic, and lyocell, vinylon, acrylic, aromatic polyamide, aromatic polyester, aromatic polyether, and the like are preferable examples. It is possible to use two or more kinds of organic fibers, but it may not always be preferable from the viewpoint of recyclability as described later.
[0015]
The diameter of the organic fiber used as the raw material is preferably 5 to 100 μm. In the sound absorbing material of the present invention, a non-fibrillated portion having a diameter of 5 to 100 μm exists in the fiber assembly, which contributes to air permeability and shape retention. When the diameter of the organic fiber as the raw material is less than 5 μm, the air permeability may be lowered and the shape retention may be deteriorated, and more preferably 10 μm or more. On the other hand, when the diameter of the organic fiber as the raw material exceeds 100 μm, there is a possibility that the sound absorption performance is lowered, and more preferably 50 μm or less. In the raw material stage, it may be a short fiber or a long fiber. Further, it may be a fabric, a sewing product, or a discarded textile product.
[0016]
The method of fibrillation is not particularly limited as long as it can partially generate ultrafine fibers. The stretched and oriented organic fibers can be fibrillated by applying a physical impact, or chemically swelled or the like. In addition, it is possible to fibrillate by splitting the composite fiber, but when splitting the composite fiber, a plurality of materials are included in the sound absorbing material, which is not always preferable from the viewpoint of recyclability. There may not be.
[0017]
Therefore, when producing the sound-absorbing material of the present invention, it is preferable to produce a short fiber by applying a physical impact to an organic fiber, in particular, an organic fiber made of a substantially single material, so as to be partially fibrillated. . Here, “substantially single” means that they are substantially the same as a material, and includes materials having slightly different brands and compositions. Thus, the sound-absorbing material excellent in recyclability can be provided by consisting of a substantially single material.
[0018]
The method for applying a physical impact is not particularly limited, and operations such as breaking, crushing, cutting, and beating can be employed. For example, the fibers can be partially fibrillated by grinding the fibers with a grinder. Also, a method of beating in water can be employed. The strength that gives physical impact varies depending on the target fiber, but by adjusting this appropriately, it is possible to balance the sound absorption performance, breathability and shape retention in the low-frequency region, which is partially fibrillated. Excellent partially fibrillated fibers can be obtained.
[0019]
The partially fibrillated fiber here is a short fiber having a portion of ultrafine fiber obtained by fibrillation and a non-fibrillated large diameter portion having a diameter of 5 to 100 μm. The thick-diameter portion may be a portion in the form of a raw material fiber, or may be a portion that maintains a diameter of 5 to 100 μm while being divided by physical impact or the like. In addition, since it is randomly cut during the fibrillation operation, the length varies greatly. However, from the balance between the sound absorption performance and the shape retention in the low frequency region, it is usually about 0.2 to 10 mm. is there. This numerical value is a rough average value of the lengths of short fibers observed with a microscope.
[0020]
Moreover, it is preferable that the diameter of the fibrillated portion is 0.1 to 4 μm and the length of the fibrillated portion is 10 μm or more. By forming fibrils having such constant dimensions, sound absorption characteristics in a low frequency region are exhibited. Such fibrils are usually formed at the ends of short fibers, but may be formed at both ends or only one end. Further, fibrils may be formed at intermediate portions that are not end portions. However, in the present invention, it is important that the ultrafine fibers formed by fibrillation are partially formed and have a portion that does not form the ultrafine fibers and remains in a large diameter. This is because such a portion can contribute to maintaining the form of the fiber assembly without causing the fibrils to fall apart into individual fibers. In the sound-absorbing material of the present invention, it is preferable that the short fiber having the above-described form is a main constituent component. Here, the main component means that more than half of the components have the above-described form on a weight basis.
[0021]
The partially fibrillated fibers thus obtained are entangled with each other to form a sheet-like aggregate, and the sound absorbing material of the present invention is obtained. The method of entanglement of the partially fibrillated fibers is not particularly limited, but a method of forming a sheet-like aggregate by making paper after stirring and dispersing in a liquid is preferably employed. Although the partially fibrillated fiber used in the present invention has fine fibril branching, the whole fiber is connected. Therefore, fine fibrils can be entangled by a method of removing liquid after entanglement in a liquid that is not easily affected by gravity, and a fiber assembly having good shape retention can be obtained.
[0022]
The liquid in which the partially fibrillated fiber is dispersed is selected according to the type of fiber to be dispersed. When the partially fibrillated fiber is a hydrophilic fiber such as cellulose fiber such as cotton, hemp, polynosic or lyocell, or vinylon, it is preferably dispersed in water. At this time, if necessary, a small amount of a surfactant may be added, or an organic solvent may be mixed and used. In addition, hydrophobic fibers such as vinylon, acrylic, aromatic polyamide, aromatic polyester, and aromatic polyether are preferably dispersed in an organic solvent. Alcohols, ketones, esters, ethers, hydrocarbons, etc. can be used as the organic solvent, but among these, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol from the viewpoint of safety and cost. Alcohols such as are preferably used. At this time, a plurality of types of organic solvents may be mixed and used, or water may be mixed and used.
[0023]
The method for stirring and dispersing the partially fibrillated fiber in the liquid is not particularly limited as long as the stirring method can uniformly disperse in the liquid. A liquid of about 10 to 1000 ml is suitably used for 1 g of partially fibrillated fibers.
[0024]
After being dispersed in this way, a sheet-like aggregate is formed by papermaking. The papermaking method is not particularly limited as long as the liquid is separated from the partially fibrillated fibers dispersed in the liquid to form a sheet-like aggregate. A liquid such as a wire mesh, cloth, filter paper, etc. can be deposited on a material through which liquid can pass and partially fibrillated fibers can be deposited thereon. From the obtained sheet-like aggregate, volatile components such as remaining water and organic solvent are removed by drying to obtain the sound-absorbing material of the present invention.
[0025]
In the sound absorbing material of the present invention, other fibers, particles, adhesives, or the like can be used as long as the effects of the present invention are not impaired. However, from the viewpoint of recyclability, it is preferable to minimize the blending of such other components. For example, fibers that are not fibrillated can be blended. In this case, it is preferable from the viewpoint of recyclability to blend fibers of substantially the same material as the partially fibrillated fibers.
[0026]
The thickness of the sound absorbing material to be obtained is not particularly limited, but is preferably 5 to 50 mm. Since the sound-absorbing material of the present invention is excellent in air permeability, it can absorb vibration energy not only on the surface of the sound-absorbing material but also on the inside thereof, and thus is suitably used as a sound-absorbing material having a relatively large thickness. The thickness at this time is measured as a thickness in a state where it is actually used as a sound absorbing material.
[0027]
A suitable apparent density of the sound-absorbing material of the present invention is 30 to 150 kg / m ³ . When the apparent density is too high, the weight of the sound-absorbing material becomes too large, and the air permeability is lowered and the sound-absorbing performance tends to be lowered. On the other hand, if the apparent density is too low, the thickness of the sound-absorbing material necessary for obtaining the desired sound-absorbing performance becomes too large, and the air-permeability increases so that the sound-absorbing performance tends to decrease. The apparent density is more preferably 40 kg / m ³ or more and 100 kg / m ³ or less.
[0028]
Moreover, it is preferable that the air permeability of the obtained sound-absorbing material is 1 to 100 cm ³ / cm ² · sec. In the sound-absorbing material of the present invention, it is preferable to use organic fibers formed with fibrils having such a degree of air permeability. If the fibrillation is insufficient, the air permeability becomes too large, and if the fibrillation proceeds excessively, the air permeability becomes too small. By setting the air permeability to 1 cm ³ / cm ² · sec or more, there is little reflection of sound waves on the surface of the sound absorbing material, and it is possible to efficiently absorb sound wave energy even inside the sound absorbing material. More preferably, it is 2 cm ³ / cm ² · sec or more, and further preferably 3 cm ³ / cm ² · sec or more. On the other hand, when the air permeability exceeds 100 cm ³ / cm ² · sec, the vibration absorption efficiency is lowered, and the necessary thickness of the sound absorbing material becomes too large, which may be uneconomical. More preferably, it is 80 cm ³ / cm ² · sec or less, and further preferably 60 cm ³ / cm ² · sec or less. The air permeability is a value measured by applying the air permeability A method (fragile type method) of JIS L 1096 “General Textile Testing Method”.
[0029]
The sound absorbing material comprising the fiber assembly thus obtained can be used alone as a sound absorbing material, but can also be used by laminating with other materials depending on the required physical properties. The sound-absorbing material of the present invention has excellent sound-absorbing properties in a wide frequency range, particularly in a low-frequency range, and is excellent in air permeability and shape retention. Therefore, it can be used for various applications that require sound absorption. For example, it can be used for various applications such as the interior and exterior of buildings, acoustic devices, and housings for noise generators.
[0030]
Even if the sound-absorbing material of the present invention is composed of a partially fibrillated fiber alone, it has an excellent balance of sound-absorbing property, air permeability and shape retention, so that a uniform quality can be obtained even when recovered and reused. Cheap. Therefore, after opening the sound-absorbing material of the present invention after use, it is a preferred embodiment to re-entangle and form a sheet-like aggregate to obtain the sound-absorbing material of the present invention again.
[0031]
The fiber material used as the raw material of the sound-absorbing material of the present invention may, of course, be a new one, but produces a short fiber that is partially fibrillated by giving a physical impact to the discarded fiber product. This is also a preferred embodiment.
[0032]
Therefore, the sound absorbing material of the present invention can be produced using waste as a raw material, and the sound absorbing material of the present invention can be collected and regenerated as a sound absorbing material again. Although the problem of recycling fiber material waste is a problem in recent years, the present invention provides a useful technique from the viewpoint of such waste recovery and reuse.
[0033]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples.
[0034]
Example 1
Cotton having a diameter of 15 to 26 μm was used as a raw material. An electron micrograph of the raw material is shown in FIG. This was put into a small fine pulverizer “SAMPLE MILL KII W-2” manufactured by Fuji Paudal Co., Ltd., pulverized, and passed through a sieve opening (circular with a diameter of 1 mm) arranged inside the pulverizer. Obtained as a pulverized product. A photograph of the obtained pulverized product observed with an electron microscope is shown in FIG. Short fibers in which fibrils are generated at the ends and the like are observed while having a portion that maintains the thickness of the entire fiber. The main fibril diameter was 0.1 to 4 μm, and the length was 10 μm or more. Such partially fibrillated short fibers are included as a main component, and the average length of the short fibers is about 0.2 to 1 mm.
[0035]
5 g of the obtained partially fibrillated fiber is put into 500 ml of water, sufficiently stirred using a stick, filtered through a Buchner funnel with 5 kinds of A filter paper, and the short fibers are deposited and sucked gently. After removing water, the sheet-like fiber aggregate was obtained by sufficiently drying at 80 ° C. using a constant temperature dryer. The obtained sheet-like fiber assembly had a diameter of 10 cm, a thickness of 1.4 cm, a weight of 5 g, and an apparent density of 45 kg / m ³ . In addition, using the “Fragile-type air permeability tester AP-360” manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd., the air permeability according to JIS L 1096 “General Textile Testing Method” is applied mutatis mutandis. Was 52 cm ³ / cm ² · sec. Further, the sound absorption characteristics measured using a 2 microphone impedance measuring tube 4206 type manufactured by Brüel & Kjær were as shown in FIG. Even if the end of the fiber assembly was pinched with a fingertip of about 1 cm, it was not damaged by its own weight, and had sufficient shape retention.
[0036]
Comparative Example 1
The same cotton used in Example 1 was cut to about 2 mm with scissors to obtain non-fibrillated short fibers. This was dispersed in water and deposited in the same manner as in Example 1 to obtain a sheet-like fiber assembly having a thickness of 3 cm, a diameter of 10 cm, a weight of 5 g, and an apparent density of 21 kg / m ³ . When the air permeability and sound absorption characteristics were measured in the same manner as in Example 1, the air permeability was 125 cm ³ / cm ² · sec, and the sound absorption characteristics were as shown in FIG. When the end of this fiber assembly was pinched with a fingertip of about 1 cm, it was broken by its own weight.
[0037]
Comparative Example 2
A filter paper (No. 5A manufactured by Advantech Toyo Co., Ltd.) was used as a sample considered to be a state in which the fibrillation of the cellulose fiber was advanced. 5 g of filter paper is put into 500 ml of water, stirred with a mixer and sufficiently dispersed in water, and then deposited in the same manner as in Example 1. The diameter is 10 cm, the thickness is 0.6 cm, the weight is 10 g, and the apparent density is 212 kg. / M ³ sheet-like fiber assembly was obtained. An electron micrograph of the sheet-like fiber assembly is shown in FIG. It is observed that the whole is composed of fine (approximately 3 μm or less) fibrillated fibers. When the air permeability and sound absorption characteristics were measured in the same manner as in Example 1, the air permeability was 0.8 cm ³ / cm ² · sec, and the sound absorption characteristics were as shown in FIG.
[0038]
As shown in FIGS. 7 and 8, the sound absorbing material made of partially fibrillated fiber of Example 1 has a lower frequency region of 1000 Hz or less than the sound absorbing material of Comparative Example 1 made of non-fibrillated fiber. The sound absorption is improved. Moreover, it can be seen that the form retention is also improved. On the other hand, as shown in FIG. 9, the sound-absorbing material of Comparative Example 2 in which fibrillation has progressed to a high degree improves the sound-absorbing property in a specific frequency region considered to be due to membrane vibration, but is too dependent on the wavelength. The sound absorption performance with a good balance over a wide frequency range could not be exhibited. This is considered to be because the frequency region for absorbing sound is narrowed because the abundance of fibrils is too much to prevent ventilation.
[0039]
Example 2
A 1.7 dtex (diameter: about 13 μm) aromatic polyamide fiber (para-aramid fiber “Technola” manufactured by Teijin Ltd.) was used as a raw material. An electron micrograph of the raw material is shown in FIG. This was pulverized in the same manner as in Example 1 to obtain a pulverized product. The photograph which observed the obtained ground material with the electron microscope is shown in FIG.5 and FIG.6. While having a portion that maintains a thickness almost comparable to the thickness of the raw material fibers, a portion in which a large number of ultrafine fibers are generated due to fibrillation is also observed. The main fibril diameter was 0.1 to 4 μm, and the length was 10 μm or more. Such partially fibrillated short fibers are contained as the main component, and the average length of the short fibers was about 0.2 to 3 mm.
[0040]
5 g of the obtained partially fibrillated fiber was put into 500 ml of ethyl alcohol, stirred thoroughly using a stick, filtered through a Buchner funnel with 5 types A filter paper, and the short fibers were deposited. After removing ethyl alcohol by suction, the sheet-like fiber aggregate was obtained by sufficiently drying at 80 ° C. using a constant temperature dryer. The obtained sheet-like fiber assembly had a diameter of 10 cm, a thickness of 0.7 cm, a weight of 4 g, and an apparent density of 73 kg / m ³ . When the air permeability and sound absorption characteristics were measured in the same manner as in Example 1, the air permeability was 12 cm ³ / cm ² · sec, and the sound absorption characteristics were as shown in FIG. Even if the end of the fiber assembly was pinched with a fingertip of about 1 cm, it was not damaged by its own weight, and had sufficient shape retention.
[0041]
Comparative Example 3
The same aromatic polyamide fiber used in Example 2 was cut to about 2 mm with scissors. This was dispersed in ethyl alcohol and deposited in the same manner as in Example 2 to obtain a sheet-like fiber aggregate having a thickness of 2.8 cm, a diameter of 10 cm, a weight of 5 g, and an apparent density of 23 kg / m ³ . When the air permeability and sound absorption characteristics were measured in the same manner as in Example 1, the air permeability was 95 cm ³ / cm ² · sec, and the sound absorption characteristics were as shown in FIG. When the end of this fiber assembly was pinched with a fingertip of about 1 cm, it was broken by its own weight.
[0042]
As shown in FIGS. 10 and 11, the sound absorbing material made of partially fibrillated fiber of Example 2 has a lower frequency range of 1000 Hz or less than the sound absorbing material of Comparative Example 3 made of non-fibrillated fiber. It can be seen that the sound-absorbing property is significantly improved. At the same time, it can be seen that the form retention is also improved.
[0043]
【The invention's effect】
The sound-absorbing material of the present invention has excellent sound-absorbing properties in a wide frequency range, particularly in a low-frequency range, and is excellent in air permeability and shape retention. It can be suitably used for various applications such as a housing. In addition, it is possible to produce a sound absorbing material from waste fiber products, and it is also possible to use the sound absorbing material after use as a new raw material for the sound absorbing material. Therefore, a sound absorbing material excellent in recyclability can be provided.
[Brief description of the drawings]
1 is an electron micrograph of raw material cotton used in Example 1. FIG.
2 is an electron micrograph of the partially fibrillated fiber obtained in Example 1. FIG.
3 is an electron micrograph of filter paper used in Comparative Example 2. FIG.
4 is an electron micrograph of the starting aromatic polyamide fiber used in Example 2. FIG.
5 is an electron micrograph (low magnification) of the partially fibrillated fiber obtained in Example 2. FIG.
6 is an electron micrograph (high magnification) of the partially fibrillated fiber obtained in Example 2. FIG.
7 is a sound absorption characteristic of the fiber assembly obtained in Example 1. FIG.
8 is a sound absorption characteristic of the fiber assembly obtained in Comparative Example 1. FIG.
9 is a sound absorption characteristic of the fiber assembly obtained in Comparative Example 2. FIG.
10 is a sound absorption characteristic of the fiber assembly obtained in Example 2. FIG.
11 is a sound absorption characteristic of the fiber assembly obtained in Comparative Example 3. FIG.

Claims (5)

A sound-absorbing material consisting of a sheet-like assembly in which organic fibers are entangled with each other,
A short fiber having a part of ultrafine fiber having a diameter of 0.1 to 4 μm and a length of 10 μm or more, and a non-fibrillated large diameter part having a diameter of 5 to 100 μm, in which the organic fiber is partially fibrillated , and the substantially comprises only organic fibers of a single material, the the thickness of the sheet-like aggregates 5 to 50 mm, and the air permeability of the sheet-like aggregates 1~100cm ³ / cm ² · A sound-absorbing material characterized by being sec.   The sound-absorbing material according to claim 1, wherein the short fibers have a length of 0.2 to 10 mm. A method for producing a sound absorbing material comprising a sheet-like assembly in which organic fibers are entangled with each other,
A short fiber having a part of ultrafine fiber having a diameter of 0.1 to 4 μm and a length of 10 μm or more, and a non-fibrillated large diameter part having a diameter of 5 to 100 μm, in which the organic fiber is partially fibrillated The organic fiber is a main constituent, the thickness of the sheet-like aggregate is 5 to 50 mm, and the air permeability of the sheet-like aggregate is 1 to 100 cm ³ / cm ² · sec ,
A sound absorbing material, characterized in that a short fiber is produced by physically pulverizing a discarded fiber product and then partially fibrillating the fiber product to form a sheet-like aggregate by entanglement of the short fibers with each other. Production method. The method for producing a sound-absorbing material according to claim 3, wherein the short fibers are stirred and dispersed in a liquid and then made into a sheet to form a sheet-like aggregate. A method for producing a sound absorbing material comprising a sheet-like assembly in which organic fibers are entangled with each other,
A short fiber having a part of ultrafine fiber having a diameter of 0.1 to 4 μm and a length of 10 μm or more, and a non-fibrillated large diameter part having a diameter of 5 to 100 μm, in which the organic fiber is partially fibrillated The organic fiber is a main constituent, the thickness of the sheet-like aggregate is 5 to 50 mm, and the air permeability of the sheet-like aggregate is 1 to 100 cm ³ / cm ² · sec ,
A method for producing a sound absorbing material, comprising: opening the sound absorbing material and then intermingling again to form a sheet-like aggregate.

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