JPH0895576A - Sound absorbing material and its production - Google Patents

Abstract

PURPOSE: To provide a sound absorbing material which exhibits good sound absorbing characteristics and to prevent the deterioration in its performance by spilling of powder by holding the powder via binders into the gaps among fibers and converting the powder into platelike powder having a specific aspect ratio. CONSTITUTION: The powder 1 of the sound absorbing material formed by holding the powder 1 via the binders 4 in the gaps among the fibers 2 is formed of the platelike powder having the aspect ratio of >=10. The aspect ratio referred to here is a numerical value obtd. by dividing the average grain size of the platelike powder by a thickness. The fibers to be used as the fibers 2 include synthetic fibers, such as polyester fibers, and inorg. fibers, such as rock fibers. The powder 1 includes mica, brass foil, graphite, etc., having a grain size of about 0.1 to 1000μm, a bulk density of about 0.1 to 1.5g/cm<2> and the aspect ratio of >=10. Further, the binders 4 include polyethylene resins, etc. The preferable mixing ratios of the fibers 2, the powder 1 or the binders 4 are 20 to 80% fibers 2 by weight and about 5 to 20wt.% binders 4 by the weight of the fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing material and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, urethane foam or glass wool has been used as a sound absorbing material.

Such a sound absorbing material is used as an interior material for a listening room, a musical instrument practice room or the like, and adjusts the reverberation time characteristic or the reflection characteristic of the room. Further, there are cases where the wall or ceiling material has a double structure for sound insulation, but it is used by being filled in the gap of this double structure to improve the sound insulation performance. In addition, it is also used for attaching inside sound-absorbing ducts and for attaching inside sound-proof covers of devices that generate noise.

By the way, in the above-mentioned urethane foam, as shown in FIG.
have. Further, in the glass wool, similarly, as shown in FIG. 6, there is a void 3 which communicates with and is complicatedly bent. The sound waves that have entered the holes 13 or the voids 3 are gradually reduced in energy due to viscous friction with the wall surface in the process of passing through a complicated and long communication path such as the holes 13 or the voids 3 and are absorbed. It is something.

[0005]

However, the sound absorption coefficient of the sound absorbing material as shown in the above-mentioned conventional example increases as the frequency increases and the thickness of the sound absorbing material increases.

That is, since the sound absorption coefficient in the low frequency range is low, sound waves in the low frequency range cannot be sufficiently absorbed unless a thick sound absorbing material is used. However, it is not preferable to increase the thickness of the sound absorbing material in order to improve the sound absorption coefficient in the low frequency region. For example, there is a problem that the room becomes narrow when it is used for interior decoration of a room, and the air passage becomes narrow when it is used for sticking inside ducts. Therefore, in any case, there are problems in improving the acoustic characteristics of the listening room, sound insulation of the wall or ceiling, and suppression of mechanical noise.

In order to improve the above-mentioned drawbacks, the inventor has proposed a sound absorbing material in which powder is held between sheet-like or mat-like fibers, and succeeded in improving the sound absorbing coefficient in the low frequency region.
However, since this powder is only held in the voids between the fibers, there is a problem in that the powder tends to spill due to vibration during handling or after construction, resulting in deterioration of sound absorption characteristics.

For this reason, a certain degree of success has been achieved in preventing spillage of powder by interposing a thermoplastic resin binder or a foaming resin binder and adhering the fibers to the powder and the fibers. However, even if such a measure is taken, spilling of the powder may occur, and the sound absorption characteristics may deteriorate.

The present invention has been made in order to solve the above problems, and its purpose is to exhibit good sound absorption characteristics even in a low frequency range, and to prevent performance deterioration due to powder spillage. Providing sound absorbing material.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 is a sound-absorbing material in which powder 1 is held in voids 3 between fibers 2 via a binder 4. It is characterized in that it is a plate-like powder having an aspect ratio of 10 or more. The aspect ratio mentioned here is a value obtained by dividing the average particle diameter of the plate-like powder by the thickness.

The organic fibers that can be used as the fibers 2 are polyester fibers, nylon fibers, polyacrylonitrile fibers, polypropylene fibers, polyethylene fibers, polyvinyl chloride fibers, and other synthetic fibers or wood fibers. Examples include natural fibers such as cotton, hemp fiber, bamboo, linter (forehead of cotton), silk and wool, and regenerated cellulose fiber such as rayon.

Examples of the inorganic fibers include rock fibers, glass fibers, alumina fibers, silicon carbide fibers, and metal fibers such as steel fibers.

The above fibers 2 may be in a disjointed state or in a sheet form. For example, it may be in a state of non-woven fabric, artificial bulp, filter paper or the like, or in a state of granular cotton or the like.

As the powder 1 to be used, the particle size is usually in the range of about 0.1 to 1000 μm, and the bulk density is in the range of about 0.1 g / cm ³ to about 1.5 g / cm ³ . The average particle diameter is divided by the thickness, that is, the aspect ratio is 10 or more.

More specifically, mica (particle size: 20-
1400μm, bulk density: 0.2-0.4g / cm ³ , aspect ratio 20-
90), brass foil (particle size: 10 to 50 μm, bulk density: 1.0 to 1.4 g
/ cm ³ , aspect ratio 50-100), graphite (particle size: 1-50 μm,
Bulk density: 0.1 to 0.3 g / cm ³ ), talc (particle size: 1 to 10 μm,
Bulk density: 0.4 to 0.8 g / cm ³ ), kaolin clay, boron nitride and the like.

As the binder 4, a resin binder such as polyethylene resin, polystyrene resin, methacrylic resin, polyurethane resin, phenol resin, urea resin, or natural starch (rice starch, corn starch,
Tapioca starch), modified starch, and starch paste.

The binder 4 can be interposed between the fiber 2 and the powder 1 by various methods.
For example, they can be mixed in the form of fine particles, or can be used by adhering the material serving as the liquid binder 4 to the fibers 2 or the powder 1 by applying the material.

The above fiber 2, powder 1 or binder 4
The mixing ratio of (2) is greatly influenced by the physical properties peculiar to each constituent material, and thus is not particularly limited, but it is desirable that the weight ratio of the fiber 2 is approximately 20 to 80%.
The amount of the binder 4 is 5 to 20% by weight with respect to the fiber 2.
The degree is desirable. When the amount of the binder 4 is more than this, the sound absorbing effect due to the vibrating action of the powder 1 becomes small, which causes deterioration of the sound absorbing performance in the low frequency range, which is not preferable.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the binder 4 is a foaming resin binder. The foamable resin binder referred to here is a resin that functions as the binder 4 in a foamed state, and that reacts by heating or the like to foam, or the mixed foam material is vaporized or decomposed. A foaming material or the like is used.

That is, in order to use the above binder 4 as a foamable resin binder, the following two methods are basically used.

(1) Method using reaction product gas (2) Method using foaming agent The method of (1) is a product released when a liquid raw material is resinified, for example, carbon dioxide gas, formaldehyde, steam. And the like are used as the foaming agent, and the foaming material is vaporized by reaction heat or heating and becomes a foamable resin binder.

The method (2) is further divided into a method using a volatile foaming agent and a method using a decomposable foaming agent. The volatile foaming agent is a gas such as carbon dioxide gas, propane, butane, ether, acetone or benzene, and such a volatile liquid is contained in the material serving as the binder 4, and the binder 4 is vaporized. It can be foamed. On the other hand, in the method of utilizing the decomposable foaming agent, the foaming agent is dispersed or dissolved in the resin material which becomes the binder 4, and then the resin material which becomes the binder 4 is foamed by heating.

In this case, as the foaming agent to be used, an inorganic compound such as ammonium carbonate or sodium bicarbonate, or an organic compound such as an azo compound, a sulfonyl hydrazide compound, a nitrozo compound or an azide compound is used.
It may be appropriately selected depending on the use conditions and the resin material to be the binder 4.

According to the third aspect of the present invention, after the binder 4 is attached to the fiber 2, the powder 1 and the fiber 2 are mixed,
The binder 4 is melted by heating to produce the sound absorbing material according to claim 1 or 2.

[0025]

According to the first aspect of the invention, the probability that the powder 1 and the fibers 2 contact each other on the flat surface of the plate-like powder is high. Therefore, many parts of the surface of the powder 1 are
Since the binder 4 is interposed between the flat plate-shaped surface and the fiber 2 to be bonded to the fiber 2, the powder 1 is easily held in the gap 3 between the fibers 2. In particular, since the plate-like powder has an aspect ratio of 10 or more and the plane surface is sufficiently wide, the probability of contact between the powder 1 and the fiber 2 is sufficiently high.

With such a structure, the powder 1 is reliably held in the voids between the fibers 2, and the presence of the powder 1 improves the sound absorption coefficient in the low frequency range.

In the second aspect of the invention, since the binder 4 occupies a wide portion of the gap 3 between the fibers 2 in a foamed state, it is easy to interpose between the fibers 2 and the powder 1. In addition, since the binder 4 is in a foamed state, the Young's modulus tends to be low, which improves the sound absorption coefficient in the low frequency range.

According to the third aspect of the invention, since the binder 4 is adhered to the surface of the fiber 2 in advance, the binder 4 is well adapted to the surface of the fiber 2. Since the fiber 2 is heated and melted in this state, the surface of the fiber 2 is easily wet, and therefore the fiber 2 is well covered with the binder 4.

[0029]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an explanatory view schematically showing the detailed structure of the sound absorbing material of this embodiment. As shown in this figure, this sound absorbing material is composed of powder 1 in a space 3 between fibers 2 and a binder 4
The powder 1 is a plate-like powder having an aspect ratio of 10 or more, preferably 60 or more. The aspect ratio mentioned here is a value obtained by dividing the average particle diameter of the plate-like powder by the thickness.

The sound absorbing material described above has an improved sound absorbing coefficient particularly in the low frequency range. Therefore, it can be used as an interior material of a listening room, a musical instrument practice room, a sound absorbing duct, and a soundproof cover of a device generating noise. It can be suitably used as a filling material for internal sticking, a sound insulation improving material such as a wall panel, and a sound insulation material such as a ceiling and a double floor.

FIG. 2 is an explanatory view of an embodiment different from the above sound absorbing material, and in this embodiment, the binder 4 is a foamable resin binder.

That is, since the binder 4 occupies a wide portion of the gap 3 between the fibers 2 in a foamed state, the binder 4 easily intervenes between the fibers 2 and the powder 1. Therefore, powder 1
Is held more stably. In addition, since it is in a foamed state, the Young's modulus is likely to be low, and thus the sound absorption coefficient in the low frequency range is improved. Therefore, it is possible to obtain a sound absorbing material that does not cause performance deterioration during construction or use and can stably exhibit a high sound absorbing coefficient particularly in a low frequency range.

Hereinafter, more specific examples will be described in detail. (Example 1) Wood fiber as the fiber 2 (fiber diameter: 50
μm) as powder 1, mica (particle size: 90 μm, bulk density: 0.37 g / cm ³ , aspect ratio 65), phenol foam resin fine particles as binder 4, and after mixing each material, at 130 ℃ By heating for several minutes, the resin binder was foamed and cured to obtain a sound absorbing material. The amount of the binder 4 was about 10% by weight of the total weight of the fiber 2 and the powder 1. The mixing weight ratio of each material is 45% by weight for the fiber 2, 45% by weight for the powder 1, and 10% by weight for the phenol foam resin fine particles.

Example 2 A brass foil (particle size:
50 μm, bulk density: 1.4 g / cm ³ , aspect ratio 60), and the mixing weight ratio of each material is as follows: fiber 2 60% by weight, powder 1 31% by weight, phenolic foamed resin fine particles 9% by weight
A sound absorbing material was obtained in the same manner as in Example 1 except that.

(Example 3) Wood fiber (fiber diameter: 50 μm) was used as the fiber 2, and mica (particle diameter: 90) was used as the powder 1.
μm, bulk density: 0.37 g / cm ³ , aspect ratio 65), and starch paste (tapioca starch) as the binder 4,
An aqueous starch solution was applied to wood fibers in advance, and the materials were mixed and heated at 130 ° C. for several minutes to cure the binder 4 and obtain a sound absorbing material. The mixing weight ratio of each material is 60% by weight of the fiber 2, 31% by weight of the powder 1 and 9% by weight of the phenol foamed resin fine particles.

Example 4 A sound absorbing material was obtained in the same manner as in Example 1 except that lock fiber (fiber diameter: 10 μm) was used as the fiber 2.

Comparative Example 1 Wood fiber (fiber diameter: 50 μm) was used as the fiber 2, vermiculite (granular powder, particle size 90 μm, bulk density: 0.37 g / cm ³ ) was used as the powder 1, and phenol was used as the binder 4. The foamed resin fine particles were selected, and after mixing the respective materials, the binder 4 was foamed and cured by heating at 130 ° C. for several minutes to obtain a sound absorbing material. The mixing weight ratio of each material is 45% by weight for fiber 2 and 45% for powder 1.
% By weight, and 10% by weight of phenol foam resin fine particles.

(Comparative Example 2) Without using the powder 1, 9 fibers 2 were used.
A sound absorbing material composed of a wood fiber and a binder 4 was obtained in the same manner as in Example 1 except that 1% by weight and 9% by weight of the phenol foam resin fine particles were used.

Comparative Example 3 A commercially available rock wool felt (density 130K) was selected as a comparative material.

With respect to the sound absorbing materials obtained in each of the above Examples and Comparative Examples, the peak frequencies of the structure retaining property and the sound absorbing coefficient were measured and evaluated. Further, a list of mixing ratios and physical properties of each material of each Example and Comparative Example is shown in Table 1 below, and evaluation results of the sound absorbing materials of these Examples and Comparative Examples are shown in Table 2 below. Shows.

[0042]

[Table 1]

[0043]

[Table 2]

The structure-retaining property shows how stably the powder 1 is retained in the voids 3 between the fibers 2, and is evaluated as follows. That is, the sound absorbing material sample was placed on a sieve, and the sieve was vibrated with a shaker for a certain period of time, and the weight reduction rate of the sample was examined.
In Table 1, those with a weight reduction rate of 3% or less are ◯, 3
.About.5% is shown as .DELTA., And 5% or more is shown as x.

The sound absorption coefficient referred to here is the JIS standard A1.
405 is the normal incident sound absorption coefficient measured according to the “method of measuring normal incident sound absorption coefficient of building material by in-pipe method”, and is measured when the sound absorbing material thickness is 30 mm. The sound absorption coefficient is calculated using standing waves.

Further, as an example, a graph obtained by measuring the sound absorption coefficient of the sound absorbing material of Example 1 is shown in FIG. 3 and that of Comparative Example 1 is shown in FIG. These graphs show the frequency dependence of the sound absorption coefficient. Further, here, the frequency at which the sound absorption coefficient is maximum is defined as the sound absorption peak frequency.

The density of each sound absorbing material was also examined, and it was 150 to 190 kg / m ³ , which was a substantially constant density.

From Tables 1 and 2, the sound-absorbing materials of all the examples have the same structure retention, the sound-absorbing peak frequency is lowered, and the low-frequency range is lower than those of the sound-absorbing materials of Comparative Examples 2 and 3. It can be seen that the sound absorption performance at is excellent. This is because the powder 1 is used for the sound absorbing material of the example, and therefore,
It shows that the sound absorption characteristics in the low range are improved.

In comparison between Example 1 and Comparative Example 1,
It can be seen that the sound absorption characteristics are almost the same, and the structure retention is better in Example 1. In Comparative Example 1, vermiculite, which is a granular powder, is used as the powder 1, whereas in Example 1, mica, which is a plate-like powder, is used. This is because 1 is reliably held via the binder 4.

That is, as the powder 1, a plate-like powder having an aspect ratio of 10 or more is used, and the binder 4 is held in the voids 3 between the fibers 2 to hold the powder 1, whereby the granular powder 1 is obtained. Therefore, the contact area between the fiber 2 and the powder 1 is increased as compared with the case of using. Therefore, the fibers 2 of the powder 1
Of the sound absorbing material obtained in Example 1 has improved structure retention.

[0051]

According to the first aspect of the present invention, by using the plate-like powder having an aspect ratio of 10 or more, the powder is reliably retained in the voids between the fibers. Therefore, during handling and after use, the powder does not separate from the voids between the fibers and is not separated by a part of the sound absorbing material, and good sound absorbing properties are always maintained stably. In particular, the presence of the powder makes it a sound absorbing material having a good sound absorbing coefficient in the low frequency region.

According to the second aspect of the invention, since the expandable resin binder is used as the binder, there is a high probability that the expandable resin binder will be present between the fiber and the powder, and therefore the powder can be retained more reliably. Therefore, the sound absorption characteristics are maintained more stably. In addition, since the Young's modulus is low, the sound absorption coefficient in the low frequency range is further improved.

In the invention according to claim 3, since the resin binder is adhered to the surface of the fiber in advance, it is heated.
When melted, the surface of the powder or fiber is well wetted. Therefore, it is possible to manufacture a sound absorbing material in which the fibers are well covered with the binder and adhered at many contact portions, and the powder is reliably held in the gaps between the fibers.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an internal structure of a sound absorbing material in an embodiment of the present invention.

FIG. 2 is an explanatory view schematically showing the internal structure of another sound absorbing material of the above-mentioned embodiment.

FIG. 3 is a graph showing the frequency dependence of the sound absorption coefficient of the sound absorbing material obtained in Example 1 of the above.

FIG. 4 is a graph showing the frequency dependence of the sound absorption coefficient of the sound absorbing material obtained in Comparative Example 1.

FIG. 5 is an explanatory view schematically showing the internal structure of a conventional sound absorbing material.

FIG. 6 is an explanatory view schematically showing the internal structure of a conventional sound absorbing material.

[Explanation of symbols]

 1 powder 2 fiber 3 voids 4 binder 13 holes

Claims (3)

[Claims] 1. A sound-absorbing material in which powder is held in voids between fibers via a binder, wherein the powder has an aspect ratio of 1
A sound-absorbing material, characterized in that it is a plate-like powder of 0 or more. 2. The sound absorbing material according to claim 1, wherein the binder is a foamable resin binder. 3. The method for producing a sound absorbing material according to claim 1, wherein after the binder is attached to the fiber, the fiber and the powder are mixed and heated to melt the binder.