JP7032032B2 - Sound absorbing felt - Google Patents

Description

The present invention relates to a felt that is thin and lightweight but has excellent characteristics required for a felt material, and is particularly suitable for use of a sound absorbing material having excellent sound absorbing characteristics from low frequencies to high frequencies. ..

There is increasing interest in improving the indoor environment in automobiles and buildings, and in particular, there is a high demand for noise control measures, and sound absorbing materials are widely used. The mechanism of sound absorption is that the air vibrated by the sound waves incident on the sound absorbing material receives viscous resistance due to collision or friction inside the sound absorbing material, is converted into heat energy and dissipated, and the sound energy is attenuated. .. For this reason, it is desirable that the structure of the sound absorbing material has a penetrating structure through which sound waves can pass, and that the specific surface area inside the sound absorbing material is increased so that the viscous resistance that the vibrating air receives during collision and friction is large. A material having a porous structure is used as a sound absorbing material.

In conventional sound absorbing materials, glass wool, rock wool, aluminum fiber, foam foam, porous ceramics, etc. are used as those having excellent sound absorbing characteristics, but there are problems in terms of health effects on the human body, recycling, and environmental compatibility. , Sound absorbing materials have been proposed to replace these materials.

Among them, non-woven fabrics formed by entwining or adhering synthetic fibers have relatively many proposals because they are inexpensive and have good moldability, in addition to overcoming the problems of conventional sound absorbing materials. In particular, the sound absorbing performance in the high frequency range improves as the sound absorbing material becomes thicker. Therefore, in the sound absorbing material made of synthetic fibers, a method of increasing the basis weight has been used as a method for improving the sound absorbing performance. However, especially in sound absorbing materials for automobiles, there is an increasing demand for lightweight and thin non-woven fabrics in order to improve fuel efficiency, and various improvements such as fiber diameter, laminated structure, and combination with different materials such as films have been made. .. Furthermore, with the spread of hybrid cars and electric vehicles in recent years, a higher level of quietness is required, and there is an increasing demand for sound absorption characteristics in the low frequency range such as road noise. Various proposals have been made to meet the demand for such sound absorbing materials.

Patent Document 1 proposes a sound absorbing material in which a nonwoven fabric made of fibers having a fineness of 1.1 to 11 dtex is used as a base material and a melt blow nonwoven fabric made of fibers having a fineness of 1.1 decitex or less is laminated. In this technology, the sound absorption performance is enhanced by the interaction between the ultrafine fiber layer and the base material layer by the melt blown non-woven fabric, which makes it possible to reduce the basis weight. Although it is thinner and lighter than the conventional sound absorbing material made of synthetic fiber, it is mainly in the high frequency range, and the sound absorbing performance is the same as the conventional one, and the sound absorbing characteristic in the low frequency range. Was not satisfactory.

Further, Patent Document 2 proposes a sound absorbing material which is lightweight, thin, and has good sound absorbing performance by laminating a porous film on a non-woven fabric as a base material. Certainly, by adopting the combination with the porous film, the sound absorbing performance at high frequencies is improved while achieving the thinness and weight reduction as compared with the conventional sound absorbing material derived from synthetic resin. However, in Patent Document 2, as in Patent Document 1, the sound absorption performance in the low frequency range corresponding to road noise and the like is insufficient.

On the other hand, Patent Document 3 proposes a sound absorbing material having a wide and good sound absorbing property from low frequency to high frequency by laminating a non-woven fabric made of micron-order ultrafine fibers on a fiber structure as a base material. .. It is difficult to improve the sound absorption performance in the low frequency range (less than 1000 Hz) by the method of increasing the basis weight, but in the low frequency range by adopting a non-woven fabric made of ultrafine fibers and devising the laminated structure of the non-woven fabric. The sound absorption performance of is improved. It is true that the sound absorption performance is improved even in the low frequency range as compared with the conventional sound absorption material made of synthetic fiber, but the sound absorption performance itself is insufficient, and it is used as a sound absorption material in automobile applications and the like. It was necessary to increase the basis weight such as laminating, and it was difficult to use it as a lightweight and thin sound absorbing material.

JP 2001-205725 (Claims) JP-A-2006-285086 (Claims) JP-A-2009-186825 (Claims)

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a sound absorbing felt which is lightweight, thin, and has excellent sound absorbing characteristics in a low frequency range.

The above object is achieved by the following means.

(1) In the felt made of synthetic fibers, the air permeability P (cc / cm ² · sec) and the texture M (g / m ² ) satisfy 1 ≦ P / M ^−0.8 ≦ 20, and the layer thickness is large. A sound absorbing felt characterized in that it is partially composed of a dense layer having a frequency of 10 mm or less and has a sound absorbing coefficient of 70% or more at a frequency of 1000 Hz.

(2) The sound absorbing felt according to (1), wherein the dense layer is composed of ultrafine fibers having a single fiber diameter of 1.0 μm or less and a fiber length in the range of 20 to 150 mm.

( 3 ) A textile product in which the sound-absorbing felt according to (1) or (2) constitutes at least a part.

The present invention relates to a sound absorbing felt that is thin and lightweight but has excellent characteristics required for a sound absorbing felt material, and is particularly suitable for use in a sound absorbing material having excellent sound absorbing characteristics from low frequencies to high frequencies. Is.

FIG. 1 is a schematic view of the sound absorbing felt of the present invention.

Hereinafter, the present invention will be described in detail together with desirable embodiments.
The sound absorbing felt of the present invention is composed of synthetic fibers, and is a dense layer having an air permeability P (cc / cm ² · sec) and a basis weight M (g / m ² ) satisfying 1 ≦ P / M ^−0.8 ≦ 1000. Needs to form at least part of it. The term "felt" as used herein refers to a non-woven fabric in which synthetic fibers are entwined by a needle punch. Further, the air permeability P is an air permeability measured by a Frazier type air permeability tester according to JIS L 1913 (2010).

The sound absorbing mechanism is such that the sound energy is attenuated by converting the air vibrated by the sound wave incident on the sound absorbing material into thermal energy by collision or friction. For this reason, the structure of the sound absorbing material has a penetrating structure through which sound waves can enter and pass through, and having air permeability is a guideline for exhibiting excellent sound absorbing characteristics. On the other hand, in order to generate a sound absorbing action, one of the mechanisms is that the incident sound wave collides with and rubs against the felt constituent fibers and is converted into thermal energy, which increases the specific surface area that can be contacted with the sound wave. It is preferable to let it. This increase in specific surface area can be achieved by increasing the felt density by reducing the fiber diameter of the constituent fibers and increasing the grain size, but if the felt density becomes too high, the sound waves will be felt. It will be reflected on the surface without being incident on the inside, and sufficient sound absorption performance may not be obtained.

As a result of diligent studies, the inventors have made a design that satisfies the above relationship between the air permeability P and the grain M in the dense layer constituting the sound absorbing felt, so that it is thin and lightweight, especially in the low frequency range. It was found that a sound-absorbing felt that exhibits high sound-absorbing performance and has excellent sound-absorbing performance over a wide frequency range can be obtained. When P / M- ^0.8 is within the above range, it has air permeability that allows sound waves to enter the dense layer, has a sufficiently high fiber filling density, and has a large specific surface area of constituent fibers that come into contact with sound waves. Therefore, acoustic energy can be efficiently converted into thermal energy, and high sound absorption performance can be obtained.

When P / M ^-0.8 is 1 or more, the fiber filling density in the dense layer is sufficiently high, the specific surface area of the fibers that can come into contact with the sound wave is large, and the sound wave is not reflected on the surface. , It is possible to secure the air permeability that can be incident on the dense layer. On the other hand, when P / M- ^0.8 is 1000 or less, the specific surface area of the fibers that can come into contact with the sound waves is high, and the fiber filling density in the dense layer is high, while having sufficient air permeability to allow the sound waves to enter. Can be secured at a high level. Therefore, the acoustic energy is efficiently converted into thermal energy by the contact with the constituent fibers, and excellent sound absorption performance is exhibited in the low frequency range.

In particular, the sound absorption performance in the low frequency range tends to be greatly affected by the specific surface area. Therefore, from the viewpoint of enhancing the sound absorption performance in the lower frequency range, the P / M ^-0.8 is preferably 500 or less, and there is a high demand for thinness and weight reduction while maintaining higher sound absorption performance. From the viewpoint of application to the application, it is more preferably 200 or less, further preferably 100 or less, and further preferably 20 or less. Since the specific surface area of the dense layer will increase, it will be possible to absorb low-frequency sounds with long wavelengths more efficiently, improve sound absorption performance in the low-frequency range, and make the sound-absorbing felt thinner and lighter. It leads to.

The sound absorbing sheet of the present invention needs to form at least a part of a dense layer having a thickness of 10 mm or less. If the thickness of the dense layer is within the range, the increase in basis weight is suppressed, which leads to the thinning and weight reduction of the sound absorbing felt. The dense layer is a part that greatly contributes to the sound absorption performance especially in the low frequency range, but since it can exhibit sufficient sound absorption performance even if the thickness is 10 mm or less, it can be made thinner and lighter while exhibiting the desired performance. You will be satisfied. In addition, if the thickness exceeds 10 mm, the density of the dense layer will inevitably become extremely high, and the action of reflecting sound waves will work. Become. On the other hand, as a guideline for the lower limit of the dense layer thickness, it is preferably 0.001 mm or more from the viewpoint of substantially maintaining the dense layer shape. Further, the dense layer of the sound absorbing sheet may be used alone, or may have a laminated structure with another fiber layer. For example, by laminating the dense layer using a felt having a lower density as a base material, the rigidity of the sound absorbing felt is increased, the vibration of the dense layer due to the incident acoustic energy is suppressed, and the energy is efficiently converted into heat energy. It will be. In addition, the sound-absorbing felt is less likely to settle, leading to improved durability. Furthermore, the sound absorption performance can be further enhanced by the interaction between the sound absorption characteristics of the dense layer and the sound absorption characteristics of the felt used for the base material. The fiber layer to be laminated is not particularly limited as long as it has a lower density than the dense layer, and the number of laminated fiber layers is not particularly limited.

The sound absorbing felt of the present invention is preferably composed of ultrafine fibers having a dense layer having a single fiber diameter of 1.0 μm or less and a fiber length in the range of 20 to 150 mm. The single fiber diameter here refers to the fiber width of 100 arbitrary single fibers measured from an image taken with an electron microscope for synthetic fibers in the dense layer of sound-absorbing felt, and the second digit after the decimal point of the average is rounded off. It is the value obtained up to the first digit after the decimal point. Further, the fiber length referred to here is a value obtained by the following method. That is, about 20 single fibers in which a load of 0.2 g / dtex was applied to the synthetic fibers used for producing the felt dense layer, the fiber length in a stretched state was measured with a ruler, and the fibers were randomly extracted. The fiber length was taken as an integer by rounding off the first digit after the decimal point of the average.

When the single fiber diameter is 1.0 μm or less in the dense layer that greatly contributes to the sound absorption performance, the fiber filling density in the dense layer is increased due to the ultrafine fiber. Therefore, the specific surface area at which the sound wave comes into contact with the constituent fibers becomes sufficiently large, and the conversion into heat energy due to collision / friction is efficiently performed, which is preferable. In particular, from the viewpoint of enhancing the sound absorption performance in the low frequency range, it is more preferable that the single fiber diameter of the ultrafine fibers constituting the dense layer is 0.7 μm or less. Further, as the diameter of the single fiber becomes smaller, dust, dirt, etc. are more likely to adhere to the felt, and the handleability in the manufacturing process deteriorates. Therefore, in the present invention, the lower limit of the diameter of the single fiber is 0.05 μm. be. Further, since the ultrafine fibers constituting the dense layer have very high uniformity of the single fiber diameter, the single fiber diameter of the constituent fibers tends to vary as compared with long fiber type non-woven fabrics such as spunbond and melt blow. The uniformity of the through hole (pore) size that affects sound absorption is increased. Therefore, it is possible to control the sound absorption characteristics more finely by designing the dense layer.

When the fiber length is within the above range, the ultrafine fibers have sufficient entanglement force to maintain the shape of the felt, and the ultrafine fibers are suppressed from falling off. It also works effectively to keep the structure of the through holes, which greatly contributes to the sound absorption performance of felt, stable. When the fiber length is larger than 20 mm, the ultrafine fibers constituting the felt are sufficiently entangled with each other, and the exfoliation of the ultrafine fibers can be suppressed. Further, since the felt form is stable, the felt structure is less likely to change with time when used as a sound absorbing material, and the sound absorbing performance can be stably maintained. In addition, when the fiber length is smaller than 150 mm, it is possible to prevent the problem that entanglement occurs in the single fiber to form a fiber mass and disturb the felt structure. Therefore, stable sound absorption performance can be exhibited. In particular, the sound absorption performance in the low frequency range is greatly affected by the felt structure. Therefore, from the viewpoint of stabilizing the sound absorption performance in the low frequency range, it is more preferable that the fiber length of the ultrafine fibers constituting the dense layer is in the range of 30 to 100 mm.

In the sound absorbing felt of the present invention, it is preferable that the dense layer is arranged on the surface layer of the felt. Since the dense layer having a large specific surface area and excellent sound absorption performance exists on the surface layer, the sound is efficiently incident on the dense layer and converted into heat energy. For example, in the case of a laminated structure, when the dense layer is sandwiched between lower density fiber layers, the traveling direction of the sound incident on the low density fiber layer becomes random, and the sound is efficient when reaching the dense layer. It becomes difficult to make the incident light well, and as a result, the sound absorption performance is lower than when the dense layer is present on the surface layer.

The sound absorbing felt of the present invention preferably has a sound absorbing coefficient of 50% or more at a frequency of 1000 Hz. The sound absorption coefficient here refers to the sound absorption coefficient measured by the vertical incident method described in the following examples. Generally, a material using a porous structure such as sound absorbing felt has a characteristic that the higher the frequency of sound, the higher the sound absorbing performance. Therefore, although high sound absorption performance can be obtained for high frequency range (short wavelength) sound, sufficient effect cannot be obtained for low frequency range (long wavelength) sound. The sound wave incident on the sound absorbing material vibrates the air in the pores and gaps of the porous material and receives viscous resistance, and the acoustic energy is converted into heat energy. However, if the wavelength of the incident sound wave is long, the vibration speed becomes slow, and as a result, the efficiency of converting acoustic energy into thermal energy decreases, and the sound absorption performance becomes low.

As a result of diligent studies, the inventors have found that a dense layer made of ultrafine fibers specifically exhibits high sound absorption performance in a low frequency range. This is because the fiber diameter is extremely thin, on the order of nanometers, so the specific surface area becomes extremely large, and the conversion efficiency from acoustic energy to thermal energy is high even for low-frequency sound waves with slow vibration rates. By becoming high. When the sound absorption coefficient at a frequency of 1000 Hz is 50% or more, it is possible to reduce noise that cannot be completely absorbed by the conventional sound absorbing material.

The higher the sound absorption coefficient with respect to noise, the more desirable it is, and the sound absorption coefficient at a frequency of 1000 Hz is more preferably 70% or more, and further preferably 80% or more. If the sound absorption coefficient is 70% or more, the noise at a frequency of 1000 Hz can be reduced, and if the sound absorption coefficient is 80% or more, the noise at a frequency of 1000 Hz is hardly felt.

The polymer used for the synthetic fiber constituting the sound absorbing felt of the present invention is not particularly limited as long as it is used for producing a general synthetic fiber, and examples thereof include polyester, polyamide, polyolefin, acrylic and the like. However, polyester is preferable. Examples of the polyester used include polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate and a copolymer thereof.
Examples of the polymer other than polyester include nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, polypropylene, polyethylene, polyphenylene sulfide, and copolymers thereof.

Further, from the viewpoint of reducing the environmental load at the time of disposal, a biodegradable polymer may be used, for example, polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polybutylene succinate carbonate, etc. Examples thereof include polybutylene adipate terephthalate and polyethylene terephthalate succinate or copolymers thereof.

The method for producing the sound absorbing felt of the present invention is not particularly limited, but an example of the method for producing the sound absorbing felt by the needle punching method is shown below.
An easily eluted polymer that can be eluted with a chemical solution is placed in the sea component, and a thermoplastic polymer is placed in the island component. The short fibers of the sea island composite fiber whose island component diameter is on the order of nanometers are first passed through a card machine and needle punched. The fiber is opened as a pretreatment for charging into the device. It is preferable that the short fibers are crimped by a crimper or the like from the viewpoint of increasing the entanglement force by the needle punch. Next, short fibers are put into the supply section of the needle punching device, and further opening and aligning are performed to form a sheet-shaped fiber web, which is made into a sheet laminated by the cross wrapper section and sent to the needle punching section. And carry. When it reaches the needle punch portion, the short fibers arranged in a sheet shape are entangled with each other by a needle that moves up and down to form a felt that becomes a precursor of a dense layer. On the other hand, the felt used as the laminated base material is similarly produced by the needle punching method using micron-order fibers composed of a single component of a thermoplastic polymer. By stacking the felt, which is the precursor of the dense layer, on the laminated base material felt and passing it through the needle punching device again, a sound absorbing felt laminated and integrated by entanglement between the felt layers can be obtained.

Next, this felt is immersed in a bath containing a chemical solution such as alkali, and the sea component of the sea-island composite fiber is dissolved and removed to expose the island component, and the ultrafine fiber having a fiber diameter on the order of nanometers is exposed in the felt dense layer. Is preferred. Further, in the step of dissolving and removing the sea component, heat is generally applied, and in addition to the generation of ultrafine fibers, the felt shrinks, so that a dense layer having a higher fiber filling density can be obtained. .. In this way, a sound-absorbing felt in which a dense layer made of ultrafine fibers and a base material felt are laminated and integrated can be obtained.

A method of removing the sea component of the Kaijima composite fiber in advance and then forming it into felt is also conceivable, but due to the increase in frictional force due to the ultrafine fiber and the influence of static electricity, a large amount of ultrafine fiber is present in the card machine and the needle punch part. It will adhere to the material, which will have an adverse effect on the manufacturing process, such as increased raw material loss, equipment failure, and large variation in the felt structure to be manufactured. Therefore, select a manufacturing method that generates ultrafine fibers after felting. Is preferable.

When the felt has a laminated structure, the felt as a base material may contain low melting point fibers, a binder, or the like from the viewpoint of suppressing peeling, and is heat-treated after being laminated with a dense layer made of ultrafine fibers. Therefore, a method of adhering or using various adhesives can also be applied. It is possible to improve the integrity of the sound-absorbing felt and prevent deterioration of sound-absorbing performance due to peeling between the dense layer and the base material.

The sound-absorbing felt of the present invention can be provided with a function depending on the intended use, and various functional agents may be added. Examples of the functional agent to be added include pigments, water repellents, water absorbents, flame retardants, stabilizers, antioxidants, ultraviolet absorbers, metal particles, inorganic compound particles, fragrances, deodorants, antibacterial agents, and gas adsorbents. And so on. Further, functional processing such as water-repellent processing, flameproof processing, flame-retardant processing, and antibacterial processing may be performed.

When the sound absorbing sheet of the present invention is used as a sound absorbing material, it exhibits high sound absorbing performance in a wide range from low frequency to high frequency, and therefore, as a sound absorbing material for various applications such as automobiles, electronic devices, buildings, and houses. It can be suitably used.

Hereinafter, the sound absorbing felt of the present invention will be specifically described with reference to examples.
The following evaluations were performed in Examples and Comparative Examples.

A. Single fiber diameter In an image of synthetic fibers in a felt dense layer taken with a Nikon electron microscope E-SEM, the fiber width is measured for any 100 single fibers, and the average second digit after the decimal point is rounded off. The value obtained up to the first digit after the decimal point was taken as the single fiber diameter.

B. Fiber length A load of 0.2 g / dtex was applied to the synthetic fibers constituting the felt dense layer, and the length of the stretched state was measured with a ruler. This was carried out for 20 randomly selected single fibers, and the value obtained by rounding off the first digit after the decimal point to an integer was taken as the fiber length.

C. The weight of the felt cut into 250 mm × 250 mm squares was weighed and converted into the weight per unit area (1 m ² ). The basis weight of the fiber sheet was obtained by rounding off the first digit after the decimal point of this converted value to obtain an integer value.

D. Air permeability According to the method described in JIS L1913 (2010), the air permeability of the dense layer produced using a Frazier type tester was measured, and the value obtained by rounding off the third decimal place to the second decimal place was obtained. The degree of ventilation was used.

E. Calculation of P / M- ^0.8 C. The basis weight obtained in the section is M (g / m ² ), D. The air permeability measured in the section was taken as P (cc / cm2 · sec), the value of P / M ^−0.8 was calculated, and the first digit after the decimal point was rounded off to obtain an integer value.

F. Dense layer thickness The thickness of the sound absorbing felt was measured using a dial thickness gauge (TECLOCK SM-114 transducer shape 10 mmφ, mesh size 0.01 mm, measuring force 2.5 N or less). The measurement was performed at any 5 points per sample, and the value obtained by rounding off the 3rd digit after the decimal point to the 2nd digit after the decimal point was taken as the thickness of the sound absorbing felt. Next, the thickness of the base material felt was measured by the same method, and the value obtained by subtracting the thickness of the base material felt from the thickness of the sound absorbing felt was taken as the dense layer thickness.

G. Sound absorption coefficient The measurement was performed using an "automatic vertical incident sound absorption coefficient measuring device" manufactured by Denshi Sokki Co., Ltd. in accordance with JIS A 1405-1 (2007) "Measuring method of vertically incident sound absorption coefficient of building materials by the in-pipe method".

Reference Example 1
Spinning at a spinning temperature of 295 ° C. using polyethylene terephthalate (PET) resin as an island component and PET (copolymerized PET) in which 10 mol% of 5-sodium sulfoisophthalic acid is copolymerized as a sea component (island component / sea component = 70/30). After melt-spinning at a speed of 1500 m / min, a sea-island composite fiber (island component diameter: 0.60 μm) having a single fiber diameter of 22 μm was produced by roll drawing. Next, the sea-island composite fiber was crimped by a crimper (crimp number: 12 threads / 25 mm) and cut (fiber length: 51 mm). This Kaijima composite fiber was passed through a card machine to open the fiber, and then charged into a needle punching device. The charged Kaijima composite fibers were further opened and aligned to form a fiber web, which was laminated at the cross wrapper portion. Next, the laminated fiber web is transported to the needle punch portion by the conveyor of the apparatus, and the fibers in the laminated web are entangled with each other by a needle (punch density: 40 lines / cm ² ) that moves up and down to form a dense layer (A). Felt (grain: 160 g / m ² ), which is a precursor of the above, was prepared.

On the other hand, using PET fibers having a single fiber diameter of 14 μm (crimp number: 12 threads / 25 mm, fiber length: 51 mm), felt (weight: 160 g / m ² ) was produced by the same method as described above. Using the felt produced from this PET fiber as the base material (B), the felt made from the Kaijima composite fiber is layered on it and passed through a needle punching device (punch density: 40 lines / cm ² ) to entangle and integrate the two felts. And obtained laminated felt.
Next, this laminated felt was immersed in a 0.2 wt% maleic acid aqueous solution and stirred at 130 ° C. for 30 minutes, then immersed in a 1 wt% sodium hydroxide aqueous solution and stirred at 75 ° C. for 40 minutes. The laminated felt after the treatment was washed with pure water to remove residual sodium hydroxide and decomposition products of the copolymerized PET, and then dried with a blower dryer (55 ° C.). By this chemical treatment, the sea component of the sea-island composite fiber is dissolved and removed, ultrafine fibers (fiber diameter 0.60 μm) are generated in the laminated felt, and the dense layer (A) is laminated on the base material (B) felt. I got the felt. This laminated felt is laminated on a felt (base material (C), grain: 400 g / m ² ) made of PET fiber (crimp number: 12 threads / 25 mm, cut length: 51 mm) having a single fiber diameter of 25 μm, and needle punched. By passing it through an apparatus (punch density: 40 / cm ² ), it was integrated and a sound absorbing felt was obtained.

The obtained sound-absorbing felt has a basis weight of 672 g / m ² (dense layer (A): 112 g / m ² , base material (B): 160 g / m ² , base material (C): 400 g / m ² ), and a thickness of 24. It was .67 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.46 mm, which contributes to making the sound absorbing felt thinner and lighter. Further, the air permeability of the dense layer was 1.92 cc / cm ² · sec, and it had a penetrating structure through which sound waves could enter and pass through. The P / M ^-0.8 represented by the texture M and the air permeability P of the dense layer is 84, and while having sufficient air permeability to allow sound waves to be incident, the fiber filling density in the dense layer is high, and the sound waves. The specific surface area of the fibers that can be contacted with the fiber was secured at a high level. Therefore, the sound energy is efficiently converted into heat energy by contact with the constituent fibers, and the sound absorption coefficient of this sound absorbing felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method is 100%, which is excellent. It demonstrated its performance.

Reference Examples 2 to 4, Examples 5 to 7
The island component diameters in the sea-island composite fiber were 1.00 μm ( Reference Example 2), 0.88 μm ( Reference Example 3), 0.74 μm ( Reference Example 4), 0.34 μm (Example 5), 0.21 μm. It was carried out according to Reference Example 1 except that it was changed to (Example 6) and 0.10 μm (Example 7).
The sound absorbing felt obtained in Reference Example 2 had a thickness of 24.93 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.72 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 22.94 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 1000. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 56%, and exhibited sufficient sound absorption performance.

The sound absorbing felt obtained in Reference Example 3 had a thickness of 24.82 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.61 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 11.47 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 500. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 72%, and exhibited good sound absorption performance.

The sound absorbing felt obtained in Reference Example 4 had a thickness of 24.78 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.57 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 4.58 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 200. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 81%, and exhibited excellent sound absorption performance.

The sound absorbing felt obtained in Example 5 had a thickness of 24.40 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.19 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 0.47 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 21. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 94%, and exhibited excellent sound absorption performance.

The sound absorbing felt obtained in Example 6 had a thickness of 24.33 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.12 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 0.12 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 5. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 96%, and exhibited excellent sound absorption performance.

The sound absorbing felt obtained in Example 7 had a thickness of 24.28 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.07 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 0.03 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 1. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 98%, and exhibited excellent sound absorption performance.

Comparative Example 1
This was carried out according to Reference Example 1 except that the island component ratio in the sea-island composite fiber was changed to 50% and the island component diameter was changed to 1.00 μm.
The sound-absorbing felt obtained in Comparative Example 1 had a thickness of 24.89 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.68 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer is 24.09 cc / cm ² · sec, and P / M- ^0.8 represented by the basis weight M and the air permeability P of the dense layer is 1050, which is extremely high in air permeability to the basis weight. The fiber filling density in the dense layer was low. Regarding this sound absorption felt, the sound absorption coefficient at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 34%, and the sound absorption performance was insufficient.

Comparative Example 2
A sound-absorbing felt was prepared by laminating and adhering a non-breathable polyethylene film to the base materials (B) and (C) felt used in Reference Example 1 instead of the dense layer.

The sound absorbing felt obtained in Comparative Example 2 had a thickness of 24.36 mm. Of these, the non-breathable polyethylene film had a thickness of 0.15 mm and had a smooth surface. The air permeability of the sound-absorbing felt is 0 cc / cm ² · sec, which is non-breathable, and P / M- ^0.8 , which is represented by the grain M and the air permeability P of the non-breathable polyethylene film, is 0 and the sound wave is a sound-absorbing felt structure. It has a structure that does not enter the inside but reflects on the surface, and the sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measurement method was 6%, and the sound absorption performance was insufficient. ..

Comparative Example 3
It was carried out according to Reference Example 1 except that the basis weight of the dense layer (A) in the sound absorbing felt was changed to 3360 g / m ² .
The sound-absorbing felt obtained in Comparative Example 3 had a thickness of 34.43 mm. Of these, the dense layer (A) had a thickness of 10.22 mm, which was a very dense felt layer. The air permeability of the dense layer is 0.01 cc / cm ² · sec, and P / M- ^0.8 represented by the texture M and the air permeability P of the dense layer is 7 and has air permeability, but the degree is extremely high. It is small, and it is presumed that a part of the sound wave is reflected on the surface without entering the inside of the sound absorbing felt structure. Regarding this sound absorption felt, the sound absorption coefficient at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 38%, and the sound absorption performance was insufficient.

Reference Examples 8 to 13
The fiber length of the Kaijima composite fiber is 30 mm ( Reference Example 8), 20 mm ( Reference Example 9), 15 mm ( Reference Example 10), 100 mm ( Reference Example 11), 150 mm ( Reference Example 12), 170 mm ( Reference Example 12). Except for the change to Example 13), it was carried out according to Reference Example 1.

The sound absorbing felt obtained in Reference Example 8 had a thickness of 24.63 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.42 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 2.12 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 92. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 92%, and exhibited excellent sound absorption performance.

The sound absorbing felt obtained in Reference Example 9 had a thickness of 24.56 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.35 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 7.01 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 306. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 76%, and exhibited good sound absorption performance.

The sound absorbing felt obtained in Reference Example 10 had a thickness of 24.49 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.28 mm, which contributes to making the sound absorbing felt thinner and lighter. Since the fiber length constituting the dense layer (A) was short, the ultrafine fibers were found to fall off from the surface, and the internal structure of the dense layer (A) was disturbed, but this was not a problem. rice field. The air permeability of the dense layer was 16.52 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 720. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 54%, and exhibited sufficient sound absorption performance.

The sound-absorbing felt obtained in Reference Example 11 had a thickness of 24.53 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.32 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 2.04 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 89. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 95%, and exhibited excellent sound absorption performance.

The sound absorbing felt obtained in Reference Example 12 had a thickness of 24.55 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.33 mm, which contributes to making the sound absorbing felt thinner and lighter. In addition, a fiber mass in which ultrafine fibers were entangled with each other was observed on a part of the surface of the dense layer (A), and a part of the internal structure of the dense layer (A) was disturbed, but there was no problem. The ultrafine fibers had a dense porous structure. The air permeability of the dense layer was 6.37 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 333. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 78%, and exhibited good sound absorption performance.

The sound absorbing felt obtained in Reference Example 13 had a thickness of 24.58 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.37 mm, which contributes to making the sound absorbing felt thinner and lighter. In addition, a large number of fiber lumps in which ultrafine fibers were entangled with each other were observed on the surface of the dense layer (A), and the internal structure of the dense layer (A) was disturbed, but the level was not a problem. The air permeability of the dense layer was 12.27 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 535. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 66%, and exhibited sufficient sound absorption performance.

Reference Examples 14 to 16
The island component of the sea-island composite fiber was changed to nylon 6 (melting point 225 ° C., Reference Example 16), polypropylene (melting point 169 ° C., Reference Example 17), polybutylene terephthalate (melting point 224 ° C., Reference Example 18), and spun. It was carried out according to Reference Example 1 except that the temperature was set to 285 ° C.

The sound absorbing felt obtained in Reference Example 14 had a thickness of 24.72 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.51 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 2.09 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 91. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 94%, and exhibited excellent sound absorption performance.

The sound absorbing felt obtained in Reference Example 15 had a thickness of 24.68 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.47 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 2.03 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 88. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 96%, and exhibited excellent sound absorption performance.

The sound absorbing felt obtained in Reference Example 16 had a thickness of 24.65 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.44 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 1.97 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 86. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 96%, and exhibited excellent sound absorption performance.

Reference Example 17
The precursor felt of the dense layer (A) was prepared by the same method as in Reference Example 1, and the marine component was removed by the precursor felt alone without laminating with the base material felt, and only the dense layer (A) was formed. Obtained a sound absorbing felt consisting of.
The obtained sound-absorbing felt had a basis weight of 112 g / m ² (only the dense layer (A)) and a thickness of 0.43 mm. The air permeability of the dense layer was 1.87 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 82. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 83%, and exhibited excellent sound absorption performance.

Reference Example 18
A felt in which the dense layer (A) was laminated on the base material (B) felt was produced by the same method as in Reference Example 1. This felt is laminated so that the dense layer (A) is in contact with the base material (C) felt, and is passed through a needle punching device (punch density: 40 lines / cm ² ) to be integrated and integrated into the base material (B) felt. A sound-absorbing felt having a structure in which a dense layer (A) was sandwiched between the base material (C) felt and the base material (C) felt was obtained.
The obtained sound-absorbing felt had a thickness of 24.69 mm. Of these, the dense layer (A) is a very thin felt layer with a thickness of 0.48 mm, which contributes to making the sound absorbing felt thinner and lighter. The air permeability of the dense layer was 20.81 cc / cm ² · sec, and P / M ^−0.8 represented by the basis weight M and the air permeability P of the dense layer was 907. This sound-absorbing felt is arranged so that the dense layer is sandwiched between low-density fiber layers, and the traveling direction of the sound waves incident on the low-density fiber layer is random. Is presumed to be lower than when the dense layer is placed on the surface layer. The sound absorption coefficient of this sound absorption felt at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 57%, and exhibited sufficient sound absorption performance.

Comparative Examples 4 to 6
Reference Material (B) Felt (Comparative Example 4), Base Material (C) Felt (Comparative Example 5), Laminated Felt of Base Material (B) and Base Material (C) (Comparison) in the same manner as in Reference Example 1. Example 6) was produced.

The base material (B) felt obtained in Comparative Example 4 had a basis weight of 160 g / m ² and a thickness of 1.21 mm. The air permeability is 85.00 cc / cm ² · sec. For reference, the basis weight of the base material ( _B ) is MB, and the _P / MB ^-0.8 calculated using the air permeability P is 4929, which is extremely high. It had a highly breathable and low density felt structure. The sound absorption coefficient at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 7%, and the sound absorption performance was insufficient.

The base material (C) felt obtained in Comparative Example 5 had a basis weight of 400 g / m ² and a thickness of 23.00 mm. The air permeability is 53.00 cc / cm ² · sec, and the basis weight of the base material ( _C ) is MC for reference, and P / MC ^-0.8 calculated using the air permeability P is ₆₃₉₆ , which is extremely high. It had a highly breathable and low density felt structure. The sound absorption coefficient at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 4%, and the sound absorption performance was insufficient.

The laminated felt of the base material (B) and the base material (C) obtained in Comparative Example 6 had a basis weight of 560 g / m ² and a thickness of 24.21 mm. The air permeability is 30.60 cc / cm ² · sec, and for reference, the basis weight of the laminated felt (B + C) is MB _{+ C} , and P / MB _{+ C} ^−0.8 calculated using the air permeability P is 4834. It had a very breathable and low density felt structure. The sound absorption coefficient at 1000 Hz measured by the vertical incident sound absorption coefficient measuring method was 8%, and the sound absorption performance was insufficient.

The sound absorbing felt of the present invention is thin and lightweight, has high sound absorbing performance in a wide range from low frequency to high frequency, and is useful as a sound absorbing material for automobiles, railways, electronic devices, buildings, houses, and the like. ..

1 Dense layer made of ultrafine fibers 2 Base material felt layer having a larger constituent fiber diameter than the dense layer of 1 3 Base material felt layer having a larger constituent fiber diameter than the base material felt layer of 2

Claims (3)

In felt made of synthetic fibers, the air permeability P (cc / cm ² · sec) and the grain M (g / m ² ) satisfy 1 ≦ P / M ^−0.8 ≦ 20, and the layer thickness is 10 mm or less. A sound absorbing felt characterized in that it is partially composed of a certain dense layer and has a sound absorbing coefficient of 70% or more at a frequency of 1000 Hz. The sound absorbing felt according to claim 1, wherein the dense layer is composed of ultrafine fibers having a single fiber diameter of 1.0 μm or less and a fiber length in the range of 20 to 150 mm. A textile product in which the sound-absorbing felt according to claim 1 or 2 constitutes at least a part.

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