JPH11133980A - Sound absorbing material and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the excellent sound absorbing characteristic, to eliminate the deterioration of the sound absorbing characteristic due to fall and deviation of the powder material, and to reduce the weight for miniaturization by forming a powder layer containing a specified ratio of powder and binder resin in a surface of a porous base material with fusion and solidification of the binder resin for fixation. SOLUTION: This sound absorbing material is obtained by forming a surface of a porous base material with a powder layer 2, which contains the powder 2a at 100 wt parts and the binder resin 2b at 0.5-40 wt parts in the solid condition, by fusing and solidifying the binder resin 2b for fixation. Namely, the powder layer 2 is fixed to the porous base material 1 by fusing and solidifying the powder with the resin binder 2 fused once by heating at a softening point or more, and the powder 2a is fused and solidified for fixation to the powder layer 2 by the fused resin binder 2b, and the power 2a is strongly fixed to the powder layer 2, and the powder layer 2 is strongly fixed to the porous base material 1. As a powder 2a, powder of talc, shirasu balloon and calcium carbonate is desirably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing noise of an automobile, a sound processing in a listening room or a musical instrument practice room, a reduction in noise propagating in an air-conditioning duct, a double wall and a ceiling, and the like. The present invention relates to a sound absorbing material used to fill a space between structural walls of a structure to enhance a sound insulating effect and a method for manufacturing the same.

[0002]

2. Description of the Related Art A sound-absorbing material is used in a listening room or a musical instrument practice room or the like where the acoustic characteristics of a room are problematic. Filling material that fills the walls and ceiling formed in the building, lining material that covers the inside of air-conditioning ducts and sound-absorbing ducts to prevent the propagation of noise, lining material that covers the inside of the soundproof cover of equipment that generates noise, It is used as a hood silencer, an engine undercover, and a dash panel silencer for reducing the engine noise of an automobile.

[0003] Sound absorbing materials used in such applications include glass wool, rock wool, polyurethane foam,
Conventionally, porous sound absorbing materials such as felt have been mainly used. These porous sound-absorbing materials have voids of complicated shape that communicate with each other, so that when sound waves enter the voids, viscous friction, etc., between the fiber surface and the urethane bubble wall during propagation in the voids Then, sound energy is absorbed in the porous material and sound is absorbed.

However, in general, the sound absorption coefficient of a porous material shows a characteristic that rises to the right with respect to frequency such that the sound absorption coefficient increases as the frequency increases, and a sufficient sound absorption coefficient can be obtained in a low frequency range. Can not. Air layer of sufficient thickness behind the sound entrance surface of the porous sound absorbing material (called the back air layer)
It is possible to increase the sound absorption coefficient in the low frequency range by securing the sound absorption material itself, but the sound absorption material itself becomes very bulky, and the thickness of the sound absorption material combined with the back air layer becomes very thick, For example, when it is used as an interior material of a room, a problem such as narrowing of the room occurs, and when it is used as an inside of a duct, a problem such as a narrow passage of air occurs. In addition, it is difficult to improve the sound absorbing characteristics of these porous sound absorbing materials within a limited thickness, and it is necessary to cope with the conventional method by increasing the density of the porous sound absorbing materials. This leads to an increase in the weight of the sound absorbing material.

On the other hand, as a sound absorbing material having excellent sound absorbing performance in a low frequency range even if it is thin, a sound absorbing material formed of a powder layer such as silica powder is provided. In this sound absorbing material,
When sound is incident on the powder layer, the powder particles vibrate, and the sound wave energy is converted into the vibration, thereby exhibiting a sound absorbing effect. However, the sound-absorbing material using this powder as a material is formed, for example, by filling a powder into a box-shaped container to form a powder layer, and covering with a film or the like having good sound wave transmission. However, depending on the mode of use, there is a problem that the powder uniformly filled in the container may gradually move and become unbalanced in the course of use, resulting in a change in the sound absorbing performance.

Therefore, it has been proposed to form a sound-absorbing material by filling and holding powder in voids of a very coarse porous material such as glass wool or rock wool. However, even in this case, even if the powder is initially uniformly filled in the voids of the porous material, the problem that the powder is gradually moved and biased in the use process and the sound absorbing performance is changed can be solved. Can not. In this work, the work of filling powder into the voids of a porous material formed of fibers such as glass wool and rock wool is performed by spraying the powder onto the porous material and vibrating the voids. However, this method has a problem that the powder soars into the air, which deteriorates the working environment and lowers the working efficiency. Furthermore, when processing a sound absorbing material filled with powder in the voids of such a porous material, for example, when cutting to a desired size, the powder will leak from the cut surface of the porous material, and the usual Methods for cutting sound-absorbing materials, such as foamed polyurethane, glass wool, rock wool, non-woven fabric,
It is not possible to carry out simple cutting using a cutter knife or scissors, such as when cutting felt etc.
Measures must be taken to prevent powder leakage.

Further, JP-A-5-323973, JP-A-6-110468, and JP-A-6-158748
Japanese Patent Application Publication No. JP-A-2006-13312 and the like provide a sound absorbing material having a structure in which a powder layer and a fiber sheet are alternately laminated. However, even in this case, the powder in the powder layer remains in a free state, and the problem due to the movement of the powder has not been solved. In contrast, Japanese Unexamined Patent Publication No.
In JP-A-39596, a sound-absorbing material is provided in which a foamable resin binder is interposed in a void of a fiber, and a powder is held by the foamable resin binder. However, in this case, if the foamable resin binder is not uniformly dispersed in the fiber, a sufficient powder holding effect cannot be obtained, and the fiber, the powder, and the foamed resin binder are simultaneously and uniformly dispersed. This is very complicated in manufacturing, and the ratio of the powder in the sound absorbing material is reduced by the foamable resin binder, which may adversely affect the sound absorbing characteristics of the powder in a low frequency range. There was also a problem.

Further, in the sound absorbing material using the powder as described above, although the sound absorbing coefficient in the low frequency range can be improved, the sound absorbing rate in the high frequency range is reduced. 1000-2000Hz, especially sensitive to human hearing
There is a problem that the sound absorption coefficient at the front and rear frequencies is reduced.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above points, and has excellent sound absorbing properties, does not cause deterioration of the sound absorbing properties due to powder falling off or unevenness, and the like. It is an object of the present invention to provide a light-weight, thin, sound-absorbing material having processability and workability equivalent to those of a conventional porous material, and a method for manufacturing the same.

[0010]

According to a first aspect of the present invention, there is provided a sound-absorbing material comprising: a powdery material and a binder resin having a solid content of 0.5 to 40 parts by weight on the surface of a porous substrate. The powder layer to be contained is formed by melting and fixing a binder resin. Claim 2
In the invention, the powder has a particle size of 0.1 to 1000 μm,
It has a bulk density of 0.1 to 1.5 g / cm ³ .

The invention according to claim 3 is characterized in that the powder is an inorganic powder. Claim 4
In the invention, the powder is at least one selected from talc, calcium carbonate, and shirasu balloon. In the invention of claim 5, the binder resin is a phenol resin, an acrylic resin,
It is characterized by being at least one selected from polyvinyl alcohol and polyvinyl acetate.

According to a sixth aspect of the present invention, there is provided a method for producing a sound-absorbing material, comprising the steps of: preparing a resin composition containing 100 parts by weight of powder and 0.5 to 40 parts by weight of a binder resin in solid content; After coating and drying on the surface of the substrate, the surface of the porous substrate is heated and pressed at a temperature equal to or higher than the softening point of the binder resin. Claim 7 of the present invention
The method for producing a sound-absorbing material according to the above, after applying a resin composition prepared by containing 100 parts by weight of powder and 0.5 to 40 parts by weight of a binder resin as a solid content on the surface of a porous substrate And hot pressing the surface of the porous substrate at a temperature equal to or higher than the softening point of the binder resin.

[0013]

Embodiments of the present invention will be described below. As the powder in the present invention, for example, gold mica,
Silica, acrylic resin, talc, calcium silicate, fluororesin, perlite, shirasu balloon, fused silica, graphite, crystalline cellulose, silicon carbide, diatomaceous earth, nylon,
Polyester, carbon fiber, titanium dioxide, calcium carbonate, polyvinyl chloride, polymethyl methacrylate, barium ferrite, silicone resin and other inorganic or organic materials can be used.

As the powder, any one or more of these can be selected and used.
It is preferable to use powder of talc, shirasu balloon or calcium carbonate. Talc powder and calcium carbonate powder are particularly effective in enhancing the sound absorption characteristics in the low frequency range, while Shirasu balloon powder has a lower sound absorption coefficient in the low frequency range than talc powder under the same conditions, but is excellent over a wide range in the mid-high range It has excellent sound absorption characteristics. Talc powder and shirasu balloon powder are relatively inexpensive, and calcium carbonate is more inexpensive, which also helps to reduce costs. Talc powder, shirasu balloon powder, and calcium carbonate powder may be used alone or in combination of two or more.

The powder has a particle size of 0.1 to 10
And the bulk density is 0.1 to 1.5 g /
It is preferable to use one having a range of cm ³ in order to form a powder layer having excellent sound absorption characteristics in a low frequency range.
That is, powder having a particle size of less than 0.1 μm is practically difficult to use, and conversely, if the particle size exceeds 1000 μm, it is difficult to obtain a sound absorbing effect by the powder. The bulk density is 0.1
When the bulk density is less than g / cm ³ , it becomes bulky and it is difficult to reduce the thickness. On the other hand, when the bulk density exceeds 1.5 g / cm ³ , it becomes difficult to obtain the sound absorbing effect of the powder.

In the present invention, as the binder resin, polyethylene resin, polystyrene resin, methacrylic resin, polyurethane resin, phenol resin, urea resin, acrylic resin, vinyl chloride resin, polyvinyl alcohol, polyvinyl acetate and the like can be used. However, it is particularly preferable to use a water-soluble resin, for example, a water-soluble phenol resin, an acrylic resin emulsion, polyvinyl alcohol, or polyvinyl acetate from the viewpoint of suppressing the discharge of the organic solvent or the working environment. In particular, phenolic resin is a thermosetting resin, so it can form a powder layer with good heat resistance, and phenolic resin and acrylic resin are insoluble in water after curing, so that powders with good water resistance A body layer can be formed, and polyvinyl acetate has a good affinity for inorganic powders, and can form a powder layer at lower cost. These binder resins can be used alone or in combination of two or more.

Then, 0.5 to 40 parts by weight of a binder resin and 40 to 300 parts by weight of a solvent are added to 100 parts by weight of the powder, and if necessary, a wetting agent and a dispersing agent are added. A resin composition can be prepared by mixing and mixing additives such as an agent, a thickener, a preservative, and an antifoaming agent. When the binder resin is water-soluble, water can be used as the solvent. For example, water is used as a solvent, and necessary amounts of a wetting agent and a dispersing agent are added in order to enhance the dispersibility of the powder and the affinity with the solvent or the porous substrate. Phenol resin, acrylic resin, polyvinyl alcohol, polyvinyl acetate, etc. as a binder resin, and further, powder such as talc, calcium carbonate, shirasu balloon, etc. is added to the solution thus obtained. By mixing, a resin composition can be obtained.

The resin composition is used as a non-woven fabric, a woven fabric,
The surface of the porous substrate 1 having voids, such as glass wool, rock wool, foamed polyurethane, and felt, is applied by spraying, brushing, or a roll coater, and the temperature is higher than the softening point of the binder resin (the melting temperature of the binder resin). By heating at the upper limit of the heating temperature (the decomposition temperature of the binder resin), as shown in FIG.
Powder 2a and resin binder 2b are provided on the surface of porous substrate 1.
It is possible to manufacture a sound-absorbing material on which a powder layer 2 made of is formed.

In the above sound absorbing material, the powder layer 2 is melt-fixed to the porous substrate 1 by the resin binder 2b once melted by heating at a temperature above the softening point, and the powder 2a is melted. The resin layer 2b is melted and fixed to the powder layer 2, and the powder 2a is firmly fixed to the powder layer 2 and the powder layer 2 is firmly fixed to the porous substrate 1. I have. For this reason, while the powder 2a to be dispersed is securely held on the porous substrate 1, the powder 1a
The binder resin is 0.5 to 100 parts by weight in solid content.
The amount of binder can be extremely reduced to 40 parts by weight.
About 2 parts by weight), and by vibrating the powders 2a and friction between the powders 2a, it is possible to effectively exhibit sound absorbing characteristics by converting sound energy into vibration energy and further into heat energy. You can do it. Further, since the powder 2a is held on the porous substrate 1 as the powder layer 2, the powder 2a does not move or flow out, and it is possible to prevent the sound absorbing performance from being changed. In addition to this, even if the sound absorbing material is cut into an arbitrary size, the powder 2a can be kept from falling off the cut surface to a minimum.

Here, if the solid content of the binder resin 2b is less than 0.5 part by weight with respect to 100 parts by weight of the powder, the ability to hold the powder 2a on the porous substrate 1 is reduced, and When the body layer 2 is formed, the powder 2a tends to fall off. Conversely, if the solid content of the binder resin 2b exceeds 40 parts by weight with respect to 100 parts by weight of the powder, sound absorption due to vibration of the powder 2a The effect is hindered, and the sound absorption characteristics particularly in the low frequency range are reduced.

After the resin composition is applied to the surface of the porous substrate 1 and then heated and melted at a temperature higher than the softening point of the binder resin as described above, first, the softening temperature of the binder resin After drying the resin composition at the following temperature, it can be performed by hot pressing the surface of the porous substrate 1 coated with the resin composition on a hot plate having a temperature equal to or higher than the softening point of the binder resin. Further, by hot pressing the surface of the porous substrate 1 coated with the resin composition on a hot plate at a temperature equal to or higher than the softening point of the binder resin,
Drying and fusion can be performed simultaneously. By performing the heating press in this manner, it is possible to bring out effective sound absorption characteristics even when the basis weight (coating amount) of the resin composition is small. That is, for example, when the porous substrate 1 is formed of a fiber material, the powder 2a adheres to the fibers by the binder resin 2b in a state before the hot pressing, so that the resin composition is used. If the basis weight is small, holes are formed in the powder layer 2 at the portion where the fiber spacing is wide, and the powder layer 2 is dispersed in both the horizontal and vertical directions. Although there is not much difference between the two, the hot pressing causes the dispersed powder layer 2 to be pressed into a flat surface, and at the same time promotes film formation by melting the binder resin 2b. By forming such a porous layer, sound absorption characteristics can be improved more than the porous substrate 1 itself.
Pressing at the time of the heating press is performed by compressing the porous substrate 1 so as to have a predetermined regulated thickness, and a small pressure is sufficient.

The thickness of the powder layer 2 varies depending on the bulk density and the amount per unit area of the powder 2a used, but it is close to the thickness predicted or calculated from the bulk density of the powder 2a. That is, it is preferable that the thickness be such that the powder 2a is packed as closely as possible in the powder layer 2. This is because, when the powder 2a is dispersed extremely widely, the ratio of the void portion between the powders 2a becomes too high, so that the powder 2a approaches a normal porous material, and good sound absorption characteristics in a low frequency range are obtained. This is because it becomes difficult to obtain.

When the surface properties of the sound absorbing material become a problem, a surface material such as paper, a resin film, or a nonwoven fabric can be attached to the surface of the powder layer 2. In applying the surface material, a resin composition is applied to the surface of the porous base material 1, then the surface material is overlaid on the surface, and hot pressing is performed to use the resin binder 2b. Can be simultaneously performed. Of course, a surface material may be attached to the sound absorbing material on which the powder layer 2 is formed, using an adhesive or the like. In attaching the surface material to the sound absorbing material as described above, it is necessary to consider that the sound absorbing characteristics are affected by the material of the surface material. That is, when a film is used as the surface material,
Depending on its thickness, sound becomes difficult to transmit, so that the film vibration of the film itself appears remarkably, which may cause a decrease in the sound absorption coefficient at a frequency other than its peak frequency, and its effect appears particularly in a high frequency range. Sometimes.

[0024]

Next, the present invention will be described specifically with reference to examples. Example 1 100 parts by weight of talc powder (bulk density: 0.4 g / cm ³ , average particle size: 18 μm), a binder resin containing an acrylic resin as a main component (“ES-1” manufactured by Chuo Rika Kogyo Co., Ltd.)
6 ": solid content of acrylic resin 46% by weight, water 54% by weight)
20 parts by weight in terms of solid content, 45 parts by weight of water, 1.2 parts by weight of a wetting agent (“Nopco Wet 50” manufactured by San Nopco) and a thickener (“Hydropalat 17” manufactured by San Nopco)
06 ") and 1.5 parts by weight of an antifoaming agent (" S "
N deformer ") in an amount of 0.02 parts by weight,
This was stirred and mixed to prepare a resin composition.

Next, polyester felt (bulk density 65
kg / m ³ , thickness 25 mm) as a porous substrate,
The above resin composition was sprayed onto the surface of the polyester felt so as to be applied at a solid content of 200 g / m ² (basis weight). After applying the resin composition in this manner, the resin composition is dried at 100 ° C. for 15 minutes with a drier, and further heated at 200 ° C. under a pressure of 100 g / cm ² for 1 minute to melt the acrylic resin. A sound absorbing material was obtained in which the powder layer formed by the above-mentioned process was melt-fixed to the surface of the polyester felt.

(Example 2) The same resin composition as in Example 1 was sprayed onto the surface of the same polyester felt as in Example 1 so as to have a solid content of 290 g / m ² (basis weight). Worked. After applying the resin composition in this manner, the resin composition is heated and pressed at a temperature of 200 ° C. and a pressure of 100 g / cm ² for 1 minute to dry the resin composition and simultaneously melt and form the acrylic resin. A sound absorbing material was obtained in which the powder layer to be melted was fixed to the surface of the polyester felt.

(Example 3) The same resin composition as in Example 1 was sprayed onto the surface of the same polyester felt as in Example 1 so as to be coated at a solid content of 540 g / m ² (basis weight). Worked. After applying the resin composition in this manner, the resin composition is dried at 100 ° C. for 15 minutes with a drier, and further heated at 200 ° C. under a pressure of 100 g / cm ² for 1 minute to melt the acrylic resin. A sound absorbing material was obtained in which the powder layer formed by the above-mentioned process was melt-fixed to the surface of the polyester felt.

(Example 4) The same resin composition as in Example 1 was sprayed onto the surface of the same polyester felt as in Example 1 so as to be coated at a solid content of 590 g / m ² (basis weight). Worked. After applying the resin composition in this manner, the resin composition is heated and pressed at a temperature of 200 ° C. and a pressure of 100 g / cm ² for 1 minute to dry the resin composition and simultaneously melt and form the acrylic resin. A sound absorbing material was obtained in which the powder layer to be melted was fixed to the surface of the polyester felt.

(Example 5) The same resin composition as in Example 1 was sprayed onto the surface of the same polyester felt as in Example 1 so as to have a solid content of 930 g / m ² (basis weight). Worked. After applying the resin composition in this manner, the resin composition is dried at 100 ° C. for 15 minutes with a drier, and further heated at 200 ° C. under a pressure of 100 g / cm ² for 1 minute to melt the acrylic resin. A sound absorbing material was obtained in which the powder layer formed by the above-mentioned process was melt-fixed to the surface of the polyester felt.

(Comparative Example 1) After coating the resin composition,
Sound absorption was performed in the same manner as in Example 1 except that a powder layer (acrylic resin was not fused) was formed on the surface of the polyester felt by drying at 00 ° C. for 15 minutes in a drier. Wood was obtained. (Comparative Example 2) After the resin composition was applied, 15
A sound-absorbing material was obtained in the same manner as in Example 2, except that a powder layer (an acrylic resin was not fused) was formed on the surface of the polyester felt by drying with a dryer for minutes. .

Comparative Example 3 After coating the resin composition,
Sound absorption was performed in the same manner as in Example 3 except that a powder layer (acrylic resin was not fused) was formed on the surface of the polyester felt by drying at 00 ° C. for 15 minutes with a dryer. Wood was obtained. (Comparative Example 4) After applying the resin composition, 15 minutes at 100 ° C.
A sound-absorbing material was obtained in the same manner as in Example 4, except that a powder layer (an acrylic resin was not fused) was formed on the surface of the polyester felt by drying with a dryer for minutes. .

Comparative Example 5 After coating the resin composition,
Sound absorption was performed in the same manner as in Example 5, except that a powder layer (an acrylic resin was not fused) was formed on the surface of the polyester felt by drying at 00 ° C. for 15 minutes in a drier. Wood was obtained. Comparative Example 6 The same polyester felt (bulk density: 65 kg / m ³ , thickness: 25 mm) as in Example 1 was used as a sound absorbing material.

Comparative Example 7 The same polyester felt (bulk density: 65 kg / m ³ , thickness: 25 mm) as in Example 1 was heated and pressed for 1 minute at a temperature of 200 ° C. and a pressure of 100 g / cm ² to obtain a sound absorbing material. And

[0034]

[Table 1]

The sound absorbing materials obtained in Examples 1 to 5 and Comparative Examples 1 to 7 were measured for sound absorption to evaluate sound absorbing characteristics. The measurement of the sound absorption coefficient was performed on a sample of the sound absorbing material having a thickness of about 25 mm based on JIS A 1405 “Method of measuring the normal incidence sound absorption coefficient of building materials by the in-pipe method”. The results are shown in FIGS. In addition, in order to prepare a sample for sound absorption measurement, the sound absorbing material of each example was 84 mmφ in diameter.
However, continuous leakage of the powder was not observed in any of the examples. Thus, it was confirmed that the powder of each of the examples did not cause the powder to fall off and maintained a stable state.

Next, the sound absorption characteristics will be compared. First, the resin layer was melt-fixed by hot pressing, and the resin layer was not hot pressed, that is, Example 1 and Comparative Example 1,
Comparing the sound absorption characteristics of Example 2 and Comparative Example 2, the results of Example 3 and Comparative Example 3, the results of Example 4 and Comparative Example 4, and the results of Example 5 and Comparative Example 5 all show that the sound absorption characteristics of Examples are generally higher. It can be recognized that the sound absorption characteristics are improved as a whole by heat-pressing and fixing the resin layer.

In comparison between Comparative Examples 1 to 5 in which a powder layer was formed on polyester felt and Comparative Example 6 in which a powder layer was not formed on polyester felt, the sound absorption measurement of Comparative Example 5 was higher than that of Comparative Example 6. Although improved, Comparative Examples 1-4
Then, the sound absorption rate has increased only slightly. this is,
By applying the resin composition of the present invention to the surface of the porous substrate to form a powder layer, it is possible to improve the sound absorption characteristics, but to obtain an effect of significantly improving the sound absorption characteristics, This shows that the powder layer needs to be formed by melting and fixing as in the present invention.

In Comparative Example 7, since the thickness was slightly reduced by the hot pressing, the sound absorption coefficient was extremely reduced. On the other hand, in the case of Examples 1 to 5, the thickness is similarly reduced by the heating press, but the sound absorption coefficient is improved. As described above, according to the present invention, the thickness can be reduced by the heating press and the sound absorbing characteristics can be improved, which is very convenient for a product.

As described above, according to the present invention, a good sound absorbing property can be obtained without increasing the thickness and capacity of the conventional sound absorbing material, and the sound absorbing property of the powder due to unevenness or unevenness of the powder can be obtained. It is possible to obtain a sound-absorbing material that does not deteriorate and has the same workability as the porous material of the base.

[0040]

As described above, the sound-absorbing material according to the first aspect of the present invention is characterized in that 100 parts by weight of powder is
A powder layer containing a binder resin in a solid content of 0.5 to 40 parts by weight is formed by melting and fixing the binder resin, and the powder is heated at a temperature equal to or higher than the softening point. Once the resin binder is melted and fixed to the resin layer by the melted resin binder, the resin layer is melted and fixed to the porous base material by the melted resin binder. It is possible to prevent the performance degradation of the characteristics and to obtain a high sound absorption characteristic in a low frequency range due to the vibration of the powder by reducing the ratio of the binder resin to the powder.

Further, according to the invention of claim 2, as the powder,
Particle size 0.1-1000 μm, bulk density 0.1-1.5
Since g / cm ³ is used, it is possible to form a powder layer having excellent sound absorption characteristics in a low frequency range while achieving a reduction in thickness. In the invention according to claim 3, since the inorganic powder is used as the powder, it is possible to form a highly flame-retardant powder layer using the non-flammable inorganic powder.

Further, according to the invention of claim 4, as the powder,
Since talc, calcium carbonate, and at least one selected from shirasu balloons are used, it is possible to form a powder layer having good sound absorption characteristics in a lower frequency range by using talc or calcium carbonate,
Further, by using a shirasu balloon, it is possible to form a powder layer having high sound absorption characteristics in a wider range.

According to a fifth aspect of the present invention, at least one selected from the group consisting of a phenol resin, an acrylic resin, polyvinyl alcohol, and polyvinyl acetate is used as the binder resin. By using a phenol resin or an acrylic resin, it is possible to form a highly water-resistant powder layer.By using polyvinyl alcohol or polyvinyl acetate, an inorganic powder layer can be formed. The affinity with the powder of the system is improved, and the powder layer can be formed at lower cost.

The method for producing a sound-absorbing material according to claim 6 of the present invention is characterized in that a resin composition prepared by containing 100 parts by weight of a powder and 0.5 to 40 parts by weight of a solid content of a binder resin is used. After coating and drying on the surface of the base material, the surface of the porous base material was heated and pressed at a temperature equal to or higher than the softening point of the binder resin, so that the application amount of the resin composition was small,
In other words, effective sound absorption characteristics can be obtained even when the basis weight of the resin layer is small.

The method for producing a sound-absorbing material according to claim 6 of the present invention is characterized in that a resin composition prepared by containing 100 parts by weight of powder and 0.5 to 40 parts by weight of a binder resin in solid content is porous. After coating on the surface of the porous substrate, the surface of the porous substrate was heated and pressed at a temperature equal to or higher than the softening point of the binder resin, so that the application amount of the resin composition was small, that is, the basis weight of the resin layer. An effective sound absorbing characteristic can be obtained even when the amount is small.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an embodiment of a sound absorbing material according to the present invention.

FIG. 2 is a graph showing the normal incidence sound absorbing characteristics of the sound absorbing materials of Example 1 and Comparative Examples 1, 6, and 7.

FIG. 3 is a graph showing the normal incidence sound absorption characteristics of the sound absorbing materials of Example 2 and Comparative Examples 2, 6, and 7.

FIG. 4 is a graph showing the normal incidence sound absorption characteristics of the sound absorbing materials of Example 3 and Comparative Examples 3, 6, and 7.

FIG. 5 is a graph showing the normal incidence sound absorption characteristics of the sound absorbing materials of Example 4 and Comparative Examples 4, 6, and 7.

FIG. 6 is a graph showing the normal incidence sound absorbing characteristics of the sound absorbing materials of Example 5 and Comparative Examples 5, 6, and 7.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Porous base material 2 Powder layer 2a Powder 2b Resin binder

Claims (7)

[Claims] 1. A powder layer containing 100 parts by weight of a powder and 0.5 to 40 parts by weight of a binder resin in a solid content is formed on the surface of a porous substrate by melting and fixing the binder resin. A sound absorbing material characterized by being formed. 2. The powder has a particle size of 0.1 to 1000 μm,
Sound absorbing material according to claim 1, bulk density, characterized in that the 0.1 to 1.5 g / cm ^3. 3. The sound absorbing material according to claim 1, wherein the powder is an inorganic powder. 4. The sound absorbing material according to claim 1, wherein the powder is at least one selected from talc, calcium carbonate, and shirasu balloon. 5. The sound absorbing material according to claim 1, wherein the binder resin is at least one selected from a phenol resin, an acrylic resin, polyvinyl alcohol, and polyvinyl acetate. 6. A resin composition prepared by containing 100 parts by weight of a powder and 0.5 to 40 parts by weight of a binder resin in a solid content is applied to the surface of a porous substrate, and dried. A method for producing a sound-absorbing material, comprising hot-pressing the surface of a porous substrate at a temperature equal to or higher than the softening point of a binder resin. 7. A resin composition containing 100 parts by weight of a powder and 0.5 to 40 parts by weight of a binder resin in solid content is applied to the surface of a porous substrate, and then the binder resin A method for producing a sound-absorbing material, which comprises hot-pressing the surface of a porous substrate at a temperature equal to or higher than the softening point.