JPH10254452A - Sound absorbing material - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To have a high sound absorbing performance especially for middle and low frequency sounds without deteriorating the advantageous properties of the fibrous sound absorbing material, and to prevent the fiber from falling off due to vibration, and to use a simple method. Provided is a sound absorbing material that can be manufactured. SOLUTION: The sound absorbing material is characterized in that a mixture of an inorganic fibrous material and fibrillated organic fibers forms a porous molded body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a felt-like or board-like sound-absorbing material used in the fields of construction, acoustic equipment and the like.

[0002]

2. Description of the Related Art A fibrous sound-absorbing material formed by combining glass fibers, rock wool, various organic fibers, and the like with a small amount of a binder is known. Fibrous sound-absorbing materials are felt-like or porous board-like, and inexpensive depending on the fiber material used, from products used at room temperature to those with high heat resistance.
There is a feature that various properties can be easily manufactured according to the application. However, the conventional fibrous sound-absorbing material has a non-flat frequency characteristic of the sound absorbing effect and shows a good sound absorbing characteristic for high-frequency sound, but has little effect on medium-low frequency sound of about 500 Hz or less. There were drawbacks (see FIG. 2). In addition, when actually attaching to a building, etc., it is necessary to increase the absorptivity of middle and low frequency sound by providing an air layer between the sound absorbing material and the wall surface. There was a drawback that the room became thick and the room became narrow. Furthermore, the conventional fibrous sound-absorbing material has a drawback that the reflection of sound is simple because the surface is made of only a fibrous material having a smooth surface, and that a high percentage of incident sound wave vibration is transmitted or reflected in the direction of the sound source. there were.

[0003] Japanese Patent Application Laid-Open No. Hei 8-91909 discloses an inorganic fiber base material and a crystal having a diameter of 0.1 mm formed by crystal growth on the fiber base material.
A sound-absorbing material comprising a needle-like crystal having a length of 1 to 0.4 μm and a length of 1 to 5 μm is described. However, this sound-absorbing material is difficult to manufacture because the needle-like crystal grows as a crystal, and the needle-like crystal easily falls off due to vibration.
There is a disadvantage that the handling is also difficult. Further, the sound absorption performance in the middle and low frequency sound range is insufficient, and particularly, the normal incidence sound absorption coefficient of 250 Hz or less is inferior and cannot be practically sufficiently satisfied. Furthermore, JP-A-6-33398 discloses that
A building material in which inorganic fibers are combined using a binder obtained by microfibrillating phosphoric acidated wood pulp until the fibrous material is destroyed is described, but this sound absorbing material can also be practically satisfactory. is not.

[0004]

SUMMARY OF THE INVENTION The present invention is an improvement of the conventional fibrous sound absorbing material, which has a high sound absorbing performance, especially for middle and low frequency sounds, without impairing the advantageous properties of the fibrous sound absorbing material. It is another object of the present invention to provide a sound absorbing material which does not fall off the fibers due to vibration and can be manufactured by a simple method.

[0005]

According to the present invention, there is provided a sound absorbing apparatus comprising: (1) a mixture of an inorganic fibrous material and a fibrillated organic fiber forming a porous molded body. Materials, (2) fibrillated organic fibers are polyvinyl alcohol fibers, aromatic polyamide fibers, polyarylate fibers, polyolefin fibers,
The sound-absorbing material according to the above (1), which is an acrylic fiber or a cellulosic fiber, and (3) the fibrillated organic fiber has a fiber opening degree of 50 to 6 in Canadian standard freeness.
(1) characterized in that the amount is 00 ml.
Or the sound absorbing material according to (2). (4) The content of the fibrillated organic fibers is 0.1 to 6 with respect to the total weight of the sound absorbing material.
(1) to (3), which is 0% by weight.
This is achieved by the sound absorbing material according to any one of the above.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a sound absorbing material comprising a mixture of an inorganic fibrous material and a fibrillated organic fiber forming a porous molded body. In the sound absorbing material of the present invention, fibrillated organic fibers are present in a relatively large communication gap similar to the inter-fiber gap in the conventional fibrous sound absorbing material. The fibrillated organic fiber of the present invention is appropriately opened and has a number of whisker-like projections on its surface, or the fiber itself has an ultrafine diameter of micron order or less. When receiving sound energy (sound waves), they vibrate together with the fibrous material as the base material, and radiate and consume the vibration energy of air as the vibration energy of the fibers. In this case, the larger the loss tangent (tan δ) of the material constituting the fiber, the greater the energy consumption and the more excellent the sound absorbing characteristics. Compared with inorganic materials such as metals and glass, organic polymer materials such as polyvinyl alcohol, polyolefin, aromatic polyamide, polyarylate, polyacrylonitrile, and cellulose exhibit a large loss tangent, so that the material of the fibrillated fiber used in the present invention is used. It is suitable as. In particular, polyvinyl alcohol is at room temperature
The loss tangent near 80 ° C. is large and most preferable. here,
Since the fibrillated organic fibers of the present invention are entangled with each other and entangled with the fibrous material of the base material, they are not dropped out of the sound absorbing material by vibration. Further, in the sound absorbing material of the present invention, the sound also hits the fibrillated organic fibers in addition to the fibrous material, and causes more complicated diffuse reflection as compared with the conventional sound absorbing material consisting of only the fibrous material, and a large energy during the reflection. Consumption occurs. Furthermore,
The fibrillated organic fibers have a large number of ultra-fine beard-like fibrils in the gaps between the base fibers, so that the flow resistance of air increases and the energy consumption further increases. As described above, the sound absorbing material of the present invention is considered to exhibit a high sound absorbing coefficient over a wide frequency range by containing a fibrillated organic fiber having a large loss tangent. Further, when an organic binder is used, the bonding between fibers becomes stronger.

Next, the fibrous material of the base material forming the sound absorbing material of the present invention will be described. As the inorganic fibrous material of the present invention, a material used as a material of a conventional fibrous sound absorbing material can be used, and can be selected according to the application. Specific examples of suitable inorganic fibrous materials include oxide fibers such as rock wool, glass fibers, silica fibers, and ceramic fibers, and inorganic fibers such as non-oxide fibers such as metal fibers and carbon fibers. Is mentioned. Since inorganic fibers are nonflammable, they are widely used for building materials, one of the most common uses of sound absorbing materials. When these fibers are selected as the base material, they can be used as building materials as non-combustible materials, quasi-non-combustible materials, and the like by appropriately adding the fibrillated organic fibers. In addition, when inorganic fibers are used, the bulk density of the sound absorbing material can be easily increased since the density is higher than that of the organic fibers, and the sound absorbing coefficient is improved according to the mass rule, which is advantageous. Organic fibers such as polyester fibers, acrylic fibers, phenol fibers, polyvinyl alcohol fibers, polyamide fibers, aromatic polyamide fibers, polyarylate fibers, polyolefin fibers, and protein fibers are selected as the base material. In such a case, it is difficult to use it as a building material because it is flammable and may emit toxic gas. Further, since the density of the organic fiber is smaller than that of the inorganic fiber, it is difficult to increase the bulk density. For this reason, the sound absorption coefficient is relatively low and disadvantageous. However, organic fiber is lightweight, and depending on the type of fiber, its price is low, its processability is good,
Since it has characteristics such as good tactile sensation, it is also possible to use a small amount of organic fibers in combination with inorganic fibers in some applications. The fiber diameter is preferably 50 μm or less, and more preferably 20 μm or less. If the fiber diameter is too large, it is difficult to obtain sufficient sound absorbing performance.

The fibrillated organic fiber used in the present invention is an organic fiber fibril having a very small diameter of several μm or less, or several μm on the surface of the fiber.
It is an organic fiber having a beard-like projection having an extremely small diameter of not more than m.
Organic fibers having fiber fibrils or whisker-like projections having a diameter of 1 μm or less are preferable because of excellent sound absorption characteristics. Examples of the fibrillated organic fibers of the present invention include polyvinyl alcohol (hereinafter abbreviated as PVA) fibers, aromatic polyamide fibers, polyarylate fibers, and the like.
Fibrillated fibers such as polyolefin-based fibers, acrylic fibers, and cellulosic fibers are exemplified, but PVA-based fibers are particularly excellent in terms of sound absorption characteristics, and are more preferable.

As a method for producing fibrillated fibers, a high-shear force can be applied at the time of fiber formation to directly obtain ultrafine fibrils. Fibril fibers can also be obtained by applying a chemical swelling force. For example, in the case of a PVA-based fiber, a PVA-based fibril fiber having a diameter of about 1 μm can be obtained by beating underwater a sea-island mixed fiber of a polymer having poor compatibility between PVA and PVA. In the case of an acrylic fiber, an acrylic fibril fiber can be obtained by blend-spinning a fibrillation aid polymer such as a polyalkylene polymer with polyacrylonitrile and beating it in water. In aromatic polyamide fibers, polyarylate fibers, polyolefin fibers, cellulosic fibers, etc., after highly orienting molecular chains, in air, water,
By applying a high shearing force in an organic solvent, it is also possible to obtain an organic fiber or a fibril fiber having a very small whisker projection of several μm or less. These fibrillated fibers can be used as a mixture of two or more kinds.

In the present invention, the degree of opening of the fibrillated fibers is not particularly limited. However, if the degree of opening is too low, a sufficient sound absorbing effect due to the vibration of the ultrafine fibril fibers or the whisker-like projections cannot be obtained. If too much, the fibrils are entangled with each other, resulting in poor dispersion. In the present invention, the opening degree is preferably 50 ml or more and 600 ml or less, more preferably 100 to 400 ml, in terms of Canadian standard freeness. The Canadian standard freeness is a value defined in a freeness test method for wood pulp JIS P8121, and a smaller value indicates a larger fibril fiber opening degree.

The amount of the fibrillated organic fibers in the sound absorbing material is 0.1 to 60% by weight, preferably 1 to 30% by weight based on the total weight of the sound absorbing material. When the content of the fibrillated organic fibers is less than 0.1%, the sound absorbing performance of the medium and low frequency sounds is not sufficient. On the other hand, when the content exceeds 60% by weight, the formability of the sound absorbing material is inferior.

Next, a method for producing the sound absorbing material of the present invention from an inorganic fibrous material and fibrillated organic fibers will be described. To produce the sound absorbing material of the present invention, three methods, a dry method, a semi-dry method, and a wet method, can be applied. In the dry method, a fibrillated organic fiber and a binder are sprayed on the inorganic fiber immediately after being formed in the fiber-making apparatus, and the deposited fiber is formed and dried. During this process, the binder cures. This manufacturing method is suitable for manufacturing a felt-like material having a small bulk density, and can be manufactured at low cost. In the semi-dry method, an inorganic fibrous material, fibrillated organic fibers and a binder are mixed in a container, and the resulting mixture is filled in a mold and dried by heating. During this process, the binder cures. This method is suitable for producing a board-like material having a large bulk density, in which the fibrillated organic fibers can be uniformly mixed as compared with the dry method. In the wet method, an inorganic fibrous material and fibrillated organic fibers are dispersed in water, a slurry of the obtained raw material mixture is placed in a mold for dehydration molding, subjected to dehydration molding, and then heated and dried. This manufacturing method is suitable when it is desired to disperse the components more uniformly.

The bulk density of the porous compact obtained by molding varies depending on the type of the inorganic fiber material used as a raw material, the ratio of the inorganic fiber material to the fibrillated organic fibers, the molding pressure, and the like. Considering sound absorption characteristics, a suitable bulk density is about 10 to 700 kg / m ^3, so it is preferable to select manufacturing conditions so as to obtain such a molded product.

At the time of molding, if necessary, for example, phenol resin, urea melamine resin, polyester resin,
Binders such as vinyl acetate resin, epoxy resin, urethane resin, acrylic resin, styrene resin, etc., for example, gelling agents such as aluminum sulfate, ammonium sulfate, etc., for example, flocculants such as polyacrylamide type, polyacrylester type, etc., molding aids Can be added.

[0015]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In these examples, the added amount of the binder and other auxiliaries indicates the amount as a solid content.

Examples 1 to 3 and Comparative Example 1 Rock wool, fibrillated polyvinyl alcohol-based fiber (having a fiber opening degree of Canadian standard freeness of 150 ml) and a polyester-based binder were stirred in water. Further, a gelling agent (aluminum sulfate) was added to cause gelation. A polyacrylamide-based coagulant was added thereto, and the mixture was poured into a mold and subjected to dehydration molding. Then, it was heated and dried to produce a felt-like sound absorbing material having a thickness of 30 mm. Also,
For comparison, a fibrous sound-absorbing material was produced in the same manner as described above except that the polyvinyl alcohol-based fiber was not blended. Raw material mix amount, bulk density and thickness of each obtained sound absorbing material 20mm
Table 1 shows the normal incidence sound absorption coefficient of Example 1 and Comparative Example 1.
1 and 2 show the normal incidence sound absorption coefficient of FIG.

[0017]

[Table 1]

From Table 1, it can be seen that the sound absorbing material of the present invention has a frequency of 500 Hz.
In the following, it is apparent that a high sound absorption coefficient is exhibited particularly at 250 Hz. 1 and 2, the sound absorbing material of Example 1 has a high sound absorption coefficient peak at around 500 Hz, which is not found in the sound absorbing material of Comparative Example 1, and the sound absorbing material of Comparative Example 1 also has a lower frequency range than that. It can be seen that the overall sound absorption coefficient is higher than that of the material.

Examples 4 to 6 Glass fiber, fibrillated aramid fiber (opening degree: 300 ml, Canadian standard freeness, 300 ml) and acrylic binder were stirred in water, and further gelled. (Aluminum sulfate) was added to cause gelation. A polyacrylamide-based coagulant was added thereto, and the mixture was poured into a mold and subjected to dehydration molding. Then, it was heated and dried to produce a felt-like sound absorbing material having a thickness of 30 mm. Table 2 shows the amounts of the raw materials, the bulk density of each obtained sound absorbing material, and the normal incidence sound absorption coefficient at a thickness of 20 mm.

[0020]

[Table 2]

According to Table 2, the sound-absorbing material of the present invention has a frequency of 500 Hz.
In the following, it is apparent that a high sound absorption coefficient is exhibited particularly at 250 Hz.

Examples 7 to 9 Ceramic fibers and fibrillated polyethylene fibers (with a fiber opening degree of Canadian standard freeness of 500 ml) were stirred in water and mixed with a polyacrylamide-based flocculant. Was added and poured into a mold, followed by dehydration molding. Then, it was heated and dried to produce a felt-like sound absorbing material having a thickness of 30 mm. Table 3 shows the amounts of the raw materials, the bulk density of each of the obtained sound absorbing materials, and the normal incidence sound absorption coefficient at a thickness of 20 mm.

[0023]

[Table 3]

From Table 3, it can be seen that the sound absorbing material of the present invention has a frequency of 500 Hz.
In the following, it is apparent that a high sound absorption coefficient is exhibited particularly at 250 Hz.

Example 10 and Comparative Example 2 A fibrillated polyvinyl alcohol fiber (having a standard freeness of Canadian standard of 170 ml) and a phenol resin dispersed in water were prepared. It was sprayed on rock wool immediately after fiberization by the device. Rock wool fleece to which polyvinyl alcohol had adhered was laminated and heated to obtain a felt-like sound absorbing material having a thickness of 50 mm. Also,
For comparison, a fibrous sound-absorbing material was produced in the same manner as described above except that the polyvinyl alcohol-based fiber was not blended. Raw material mixing amount, bulk density and thickness of each obtained sound absorbing material 50mm
Table 4 shows the normal incidence sound absorption coefficient at.

[0026]

[Table 4]

As shown in Table 4, the sound absorbing material of the present invention was 500 Hz
In the following, it is apparent that a high sound absorption coefficient is exhibited particularly at 250 Hz.

[0028]

As described above, the sound-absorbing material of the present invention has a remarkably improved sound absorption coefficient for middle and low frequency sounds as compared with the conventional fibrous sound-absorbing material. Therefore, if the sound absorbing material of the present invention is used, the construction efficiency is improved as compared with the case where the conventional fibrous sound absorbing material is used, or the thickness of the sound absorbing material layer in a building or the like is reduced or the construction is simplified. be able to.

[0029]

[Brief description of the drawings]

FIG. 1 is a graph showing the normal incidence sound absorption coefficient with respect to each frequency in the sound absorbing material of Example 1.

FIG. 2 is a graph showing the normal incidence sound absorption coefficient for each frequency in the sound absorbing material of Comparative Example 1.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Nishimoto 1-70, Ogurocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Within Nichias Corporation (72) Inventor Haruko Hamana 1-70, Ogurocho, Tsurumi-ku, Yokohama-shi, Kanagawa Nichias Inside the corporation

Claims (4)

[Claims] 1. A sound absorbing material comprising a mixture of an inorganic fibrous material and fibrillated organic fibers forming a porous molded body. 2. The fiber according to claim 1, wherein the fibrillated organic fibers are polyvinyl alcohol fibers, aromatic polyamide fibers, polyarylate fibers, polyolefin fibers, acrylic fibers, and cellulose fibers. Sound absorbing material. 3. The sound-absorbing material according to claim 1, wherein the degree of opening of the fibrillated organic fibers is 50 to 600 ml in Canadian standard freeness. 4. The method according to claim 1, wherein the content of the fibrillated organic fibers is 0.1 to 60% by weight based on the total weight of the sound absorbing material. Sound absorbing material.