JPH1158571A - Sound absorbing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sound absorbing material having high sound absorbing effect and reductions in weight and cost. SOLUTION: The sound absorbing material comprises a fiber aggregate obtained by laminating a nonwoven web (B layer) containing short fiber B having 2 denier or less and smaller size than that of short fiber A having 2 to 15 denier and binder fiber on one side surface of a nonwoven web (A layer) containing the short fiber A and binder fiber so that the fibers are adhered to one another by melting binder components. In this case, a thickness of the aggregate is 5 mm or more, and an apparent density is 0.01 g/cm<2> or more.

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 made of a fiber assembly, and more particularly to a sound absorbing material suitable for an automobile.

[0002]

2. Description of the Related Art The use of sound-absorbing materials for absorbing and preventing engine sounds and the like has increased due to the recent trend toward high-end vehicles. On the other hand, in order to mount the sound absorbing material on an automobile, it is important to be lighter and cheaper.

[0003] Conventionally, typical examples of sound absorbing materials for automobiles include resin felt and foamed polyurethane.
However, since resin felt contains a binder resin such as a phenol resin, it has been difficult to obtain a high sound absorbing effect relative to the weight. Further, since polyurethane foam uses a urethane foam material as a raw material, exhaust equipment is required at the time of production, and further, there is a drawback that recycling is difficult.

To solve these problems, Japanese Patent Laid-Open No.
3599 and JP-A-8-188951,
A sound absorbing material comprising a fiber aggregate in which short fibers of 1.5 denier or more are bonded with binder fibers is disclosed.

[0005] JP-A-7-3599, JP-A-8-1
A sound absorbing material composed of a fiber aggregate in which the fineness of the constituent fibers exceeds 1.5 denier in the method disclosed in Japanese Patent No. 88951 does not yet provide a sufficient sound absorbing effect, and relies on an increase in thickness and density. I have no choice. Accordingly, there is a problem that the occupied space and the weight increase accordingly.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a sound absorbing material capable of solving the contradictory problems of a high sound absorbing effect and a reduction in weight and cost.

[0007]

The present inventors have conducted various studies to obtain a sound-absorbing material capable of achieving a high sound-absorbing effect, light weight and low cost. As a result, short fibers having a small fineness were used as the main fibers. It has been found that the use of the fiber aggregate exerts a high sound absorbing effect. In addition, a fiber aggregate having mainly short fibers with small fineness as a main fiber is used in combination with fibers with large fineness to impart rigidity to the sound absorbing material, and at that time, when fibers with small fineness are concentrated on the sound absorbing surface side, The present inventors have found that the sound absorbing effect is higher than simply mixing cotton having a small fineness and a fiber having a large fineness, and arrived at the present invention. That is, the present invention provides
On one side of a nonwoven web (layer A) comprising 5 denier short fibers A and binder fibers, a nonwoven web comprising short fibers B having a denier of 2 denier or less and a fineness smaller than short fibers A and binder fibers ( B layer) is laminated, and the binder fiber has at least a binder component having a melting point or softening point lower than that of the short fiber A and the short fiber B by 20 ° C. or more on the fiber surface. The fiber aggregate has a thickness of 5 mm or more and an apparent density of 0.01 g / cm.
^The gist is a sound absorbing material characterized by being ³ or more.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, the constituent fibers of the present invention will be described. The main short fibers (short fibers A and B in the present invention are collectively referred to as main short fibers) and binder fibers used in the present invention are polyester-based polymers, polyamide-based polymers,
It is made of a fiber-forming thermoplastic polymer such as a polyolefin polymer.

Examples of the polyester polymer include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalene-2,6-dicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and esters thereof. And a homopolyester polymer containing a diol compound such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, or 1,4-cyclohexanedimethanol as a diol component, or other acid components having these as a main skeleton. Examples include a polyester copolymer obtained by copolymerizing another glycol component. In addition, paraoxybenzoic acid, 5-sodium sulfoisophthalic acid, polyalkylene glycol, pentaerythritol, bisphenol A, and the like may be added or copolymerized to these homopolyester polymers and polyester copolymers.

Examples of polyamide polymers include polyimino-1-oxotetramethylene (nylon 4), polytetramethylene adipamide (nylon 46), polycapramid (nylon 6), polyhexamethylene adipamide (nylon 66), Polyundecanamid (nylon 11),
Examples include polylaurolactamide (nylon 12), polymethaxylene adipamide, polyparaxylenedecanamide, polybiscyclohexylmethanedecanamide, or a polyamide copolymer containing these monomers as constituent units. In particular, in the case of polytetramethylene adipamide, a polytetramethylene adipamide is copolymerized with other polyamide components such as polycapramide, polyhexamethylene adipamide, and polyundecamethylene terephthalamide in an amount of 30 mol% or less. It may be a tetramethylene adipamide copolymer. When the copolymerization ratio of the other polyamide component exceeds 30 mol%, the melting point of the copolymer decreases, so that when a sound absorbing material composed of a fiber assembly of these copolymers is used under high-temperature conditions, This is not preferred because the mechanical properties and dimensional stability are reduced.

The polyolefin polymers include aliphatic α-monoolefins having 2 to 18 carbon atoms, for example, ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, -Octene, 1-
Homopolyolefin polymers composed of dodecene, 1-octadecene and the like can be mentioned. These aliphatic α-monoolefins include, for example, butadiene, isoprene, 1,3-
It may be a polyolefin-based copolymer obtained by copolymerizing other similar ethylenically unsaturated monomers such as pentadiene, styrene and α-methylstyrene. In the case of a polyethylene polymer, ethylene may be copolymerized with propylene, 1-butene, 1-hexene, 1-octene or a similar higher α-olefin at 10% by weight or less. , In the case of a polypropylene polymer, ethylene or similar higher α-
The olefin may be copolymerized at 10% by weight or less. If the copolymerization ratio of the higher α-olefin or the like exceeds the above-mentioned weight%, the melting point of the copolymer is lowered, so that a sound absorbing material comprising a fiber assembly of these copolymers is used under high temperature conditions. In such a case, the mechanical properties and dimensional stability decrease, which is not preferable.

The fiber-forming thermoplastic polymer has
If necessary, various additives such as matting agents, pigments, flame retardants, deodorants, light stabilizers, heat stabilizers, antioxidants, etc. may be added within a range that does not impair the effects of the present invention. Good.

The main short fiber used in the present invention is composed of the above-mentioned fiber-forming thermoplastic polymer, and the form thereof is selected from the above-mentioned polymers in addition to the above-mentioned polymer alone. Alternatively, two or more different polymers may be formed of a blend in which the melt spinnability is not impaired. The polymer composed solely of the polymer is preferably composed of polyethylene terephthalate from the viewpoint of high crystal melting point and economy. Examples of the blend include a blend of a polyester polymer and a polyolefin polymer, and a blend of two different polyamide polymers. This is preferable because shrinkage of the unoriented polyester component can be suppressed immediately after spinning.

The binder fiber used in the present invention is a fiber having at least a binder component having a melting point or softening point lower than the main short fiber by 20 ° C. or more on the fiber surface,
The binder component bonds the constituent fibers together by heat melting. The binder component needs to have a melting point or softening point lower than the main short fiber by 20 ° C. or more. If the difference between the two is less than 20 ° C., it is not preferable because even the main short fibers may be softened and melted when the binder component is melted by heat.

The binder fiber may be in any form as long as it has a binder component at least on the surface of the fiber, such as a single-phase binder composed of only the binder component, a laminated type of the binder component and another polymer, and a binder. A core-sheath type in which the component is disposed in the sheath and another polymer is disposed in the core may be used. In the present invention, a core-sheath type composite fiber in which a polymer (binder component) having a melting point or a softening point lower by 20 ° C. or more than the polymer arranged in the core is arranged in the sheath is preferably used. The core-sheath type conjugate fiber is preferable because only the sheath part functions as a binder for bonding the constituent fibers together, and the core part maintains the form of the fiber, which contributes to the improvement of the sound absorbing effect.

As the sound-absorbing material of the present invention, the main short fiber is made of polyethylene terephthalate, the binder fiber is polyethylene terephthalate in the core and terephthalic acid / isophthalic acid in the sheath is a copolymerization ratio (molar ratio) of 60/40 to 90.
It is preferable that the fiber aggregate is made of a core-sheath composite fiber in which a copolymerized polyester copolymerized at / 10 is disposed.
When a short fiber made of polyethylene terephthalate having a high crystal melting point and good productivity is used as the main short fiber, by using the copolymerized polyester as a binder component, the adhesiveness between constituent fibers becomes good and the form retention is good. A fiber assembly is obtained. Further, as the sound absorbing material of the present invention, a core-sheath composite in which the main short fiber is made of polyethylene terephthalate, the binder fiber is polyethylene terephthalate in the core and the ε-caprolactone copolymer polyester having a crystal melting point of 100 ° C. or more in the sheath is used It is preferably a fiber assembly made of fibers. Crystal melting point 100 ° C
Since the above-mentioned ε-caprolactone copolymerized polyester is crystalline and has a high melting point, a fiber assembly using the same as a binder component is capable of melting the binder component even when used in a high temperature state, for example, in a car in summer. However, since the sound absorbing material can maintain its shape, it is preferable that the sound absorbing material also has heat resistance.

As the ε-caprolactone copolymerized polyester, those obtained by copolymerizing an ethylene terephthalate unit and / or a butylene terephthalate unit with an ε-caprolactone unit are suitable. It does not matter whether the copolymer is a random copolymer or a block copolymer. Further, isophthalic acid, naphthalene-2,6-dicarboxylic acid, adipic acid, sebacic acid, ethylene glycol, 1,6-hexanediol and the like were additionally copolymerized with ethylene terephthalate units and / or butylene terephthalate units. Those obtained by copolymerizing ε-caprolactone units may be used. The proportion of the acid component or glycol component to be additionally copolymerized is desirably 20 mol% or less based on the number of moles of the polyester constituting component.

Among the main short fibers used in the present invention, the fineness of the short fibers A used in the nonwoven web (A layer) is 2 to 2.
Must be 15 denier. Non-woven web (layer A)
Has a sound absorbing effect, but acts as a reinforcing material for the nonwoven web (layer B), i.e., a layer composed of short fibers B having a small fineness and binder fibers, thereby improving the shape retention and rigidity of the sound absorbing material. . Therefore, if the fineness of the short fiber A is less than 2 denier, the shape retention property sufficient to reinforce the layer B is not sufficient, and it is difficult to improve the rigidity of the sound absorbing material, which is not preferable. On the other hand, if the fineness of the short fiber A exceeds 15 deniers, a sufficient sound absorbing effect cannot be obtained, and it is necessary to further increase the thickness and density of the sound absorbing material in order to improve the sound absorbing performance. It is not preferable because a material cannot be obtained. For the above reasons, the fineness of the short fiber A is preferably 4 to 13 denier, more preferably 6 to 13 denier.
10 denier.

Among the main short fibers used in the present invention, the fineness of the short fiber B used for the nonwoven web (layer B) must be 2 denier or less and the fineness must be smaller than the short fiber A. . If the fineness of the short fiber B exceeds 2 denier, the sound absorbing effect becomes insufficient, and it is necessary to increase the thickness and density of the sound absorbing material in order to improve the sound absorbing performance. Not preferable because it cannot The lower limit of the fineness is not particularly limited, but is preferably about 0.2 denier. If the denier is less than 0.2 denier, the fiber is liable to be insufficiently opened at the time of forming the web by the card machine, and therefore, there is a tendency that a nep is generated and density unevenness occurs on the web. For the above reasons, the preferred fineness of the main short fiber is 0.2 to 1.5 denier, more preferably 0.5 denier.
~ 1 denier.

The fineness of the binder fiber used in the present invention is as follows:
About 1 to 4 denier is preferable. If the fineness is less than 1 denier, it becomes difficult to produce a core-sheath type composite fiber suitable for the present invention. On the other hand, when the fineness exceeds 4 denier, the sound absorption performance tends to be inferior as in the case of the main short fiber. For the above reasons, the more preferable fineness of the binder fiber is 1 to
It is 2 denier, more preferably 1.5 to 2 denier.

The cross-sectional shapes of the main short fibers and the binder fibers are not particularly limited, and may be irregular cross-sections such as a triangular cross-section, a multi-leaf cross-section, or a hollow cross-section other than the round cross-section.

The sound-absorbing material of the present invention is a nonwoven web (layer A) comprising 2 to 15 denier short fibers A and binder fibers.
A nonwoven web (B layer) composed of a short fiber B having a denier of 2 denier or less and a fineness smaller than that of the short fiber A and a binder fiber and a binder fiber is laminated on one side of Become. Non-woven web (layer B)
A non-woven web (layer B) is laminated on both sides of the non-woven web (layer A) depending on the application, so that the non-woven web (layer A) is laminated on both sides of the fiber assembly. It may be a sound absorbing material capable of absorbing sound.

The sound-absorbing material of the present invention is a fiber assembly in which the thickness of the nonwoven web (layer B) which mainly exhibits a sound-absorbing effect occupies １ ／ to （(thickness ratio) of the thickness of the entire sound-absorbing material. Preferably, there is. When the thickness occupied by the layer B is less than 1/8, the sound absorbing effect of the fiber having a small fineness (short fiber B) is not sufficiently exhibited, and the sound absorbing performance tends to be inferior. Meanwhile, 1
If the ratio exceeds / 2, the sound absorbing effect of the short fiber B cannot be expected any more, and the shape retention tends to be poor. For the above reasons, it is particularly preferable that the thickness of the layer B is 1/4 to 1/2 (thickness ratio).

The ratio of the fibers used in the fiber assembly of the present invention is as follows: short fiber A / short fiber B / binder fiber is 30 to 70%.
/ 10 to 40/10 to 40 (% by weight). If the short fiber A is less than 30% by weight, the shape retention tends to be poor, and if it exceeds 70% by weight, the sound absorbing performance becomes insufficient. If the short fiber B is less than 10% by weight, the sound absorbing effect is not sufficiently exhibited, and the sound absorbing performance of the sound absorbing material cannot be improved. Although the higher the proportion of the short fibers B, the higher the sound absorbing performance, the upper limit is preferably 40% by weight in consideration of the shape retention of the sound absorbing material. If the proportion of the binder fiber is less than 10% by weight, the number of bonding points between the constituent fibers decreases, and the rigidity and morphological stability of the fiber assembly are undesirably reduced. On the other hand, if the mixing ratio of the binder fiber exceeds 40% by weight, the ratio of the binder component melted at the time of thermoforming increases, which undesirably impairs the sound absorbing effect of the fiber. In consideration of sound absorption performance and form stability, the ratio of the fibers used in the fiber assembly is such that the short fiber A / short fiber B / binder fiber is 40 to 60/20.
It is particularly preferable that the ratio is from 40/20 to 30 (% by weight).

The thickness of the sound absorbing material is 5 mm or more,
40 mm is preferred. If the thickness of the sound absorbing material is less than 5 mm, sufficient sound absorbing performance cannot be obtained, which is not preferable. The upper limit of the thickness of the sound absorbing material is not particularly limited, but is set to about 50 mm in consideration of the occupied space and weight of the sound absorbing material, the apparent density, and the like.

The apparent density of the sound absorbing material is 0.01 g / cm
³ or more. The apparent density of the fiber aggregate is 0.01 g /
If it is less than cm ³ , sufficient sound absorbing performance cannot be obtained because the number of constituent fibers is small, and it is difficult to secure the thickness of the fiber aggregate. The upper limit is not particularly limited, but is about 0.08 g / cm ^{3 in} consideration of the weight of the sound absorbing material. If it exceeds 0.08 g / cm ³ , not only the basis weight is increased, but also the improvement in the sound absorbing effect is hardly observed. For the above reasons, the apparent density of the sound absorbing material is 0.02 to 0.06.
g / cm ³ is preferred.

[0027]

The sound-absorbing material comprising the fiber assembly of the present invention is a material in which fibers having a small fineness are concentrated on at least one surface of the fiber assembly. It is presumed that fibers having a small fineness have low rigidity of the fibers and easily convert vibration energy of sound into heat energy. Furthermore, when fibers having a small fineness are used, it is considered that the number of constituent fibers per unit weight increases, the contact area with air increases, and the sound absorbing effect increases. Therefore, a high sound absorbing effect is exhibited by setting the surface on which fibers having a small fineness are concentrated to the sound absorbing surface side.

Further, by arranging a non-woven web made of fibers having a large fineness, it is possible to reinforce the layer made of the fibers having a small fineness and to impart shape retention and rigidity to the sound absorbing material. In addition, since fibers having high fineness have excellent shape retention, a certain thickness can be ensured even at a low density, so that a sound absorbing effect due to the thickness can be expected and the weight of the sound absorbing material can be reduced.

That is, the sound-absorbing material of the present invention is obtained by using fibers having a large fineness together with a fiber aggregate mainly comprising short fibers having a small fineness and intensively disposing the fibers having a small fineness on the sound absorbing surface side. Higher sound absorbing effect than simply mixing short fibers with small fineness and fibers with large fineness is obtained, and the same sound absorbing effect as a fiber aggregate consisting only of fibers with small fineness is obtained, while maintaining shape retention and rigidity. Will also be excellent.

In the sound-absorbing material of the present invention, since the main short fibers are bonded by hot-melting of the binder fibers, the fibers are point-bonded, and the sound-absorbing effect of the fibers can be fully utilized.

[0031]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. Each characteristic value described in the examples was measured by the following method. (1) Thickness (mm): 99.9 mm using a large thickness measuring device for foam (FS-250 type manufactured by Kobunshi Keiki Co., Ltd.)
The thickness of the φ sample was measured by applying a load of 49 g / 15 cm ² .

(2) Apparent density (g / cm ³ ): The apparent density of the fiber assembly is obtained by punching out each sound absorbing material made of the obtained fiber assembly into a sample having a diameter of 99.9 mmφ.

[0033]

(Equation 1)

(3) Relative viscosity: A sample concentration of 0.5 g / d was prepared by using an equal weight mixture of phenol and ethane tetrachloride as a solvent.
1, measured at a temperature of 20 ° C.

(4) Melt index (g / 10
Min): Measured by the method described in ASTM D1238 (E).

(5) Melting point (° C.): A differential scanning calorimeter DSC-7 manufactured by PerkinElmer Co., Ltd.
It was measured at 0 ° C./min.

(6) Normal incidence sound absorption coefficient (%): JIS
The measurement was performed using a two-microphone impedance measuring tube (Model 4206, manufactured by Brüel & Kjær) based on A1405 "Method of measuring normal incidence sound absorption coefficient of building material by in-tube method". For each of the obtained sound absorbing materials, a low frequency (50
Hz to 1.6 kHz) 99.9 mmφ size for pipes and 29.0 mmφ for high frequency (500 Hz to 6.4 kHz) pipes
Two sizes were measured, and the average value of the two sizes was used as the normal incidence sound absorption coefficient in the overlapping measurement frequency region.

Example 1 As a short fiber A, a fineness of a hollow section made of polyethylene terephthalate (relative viscosity 1.38, melting point 257 ° C.) 6
Denier, a fiber with a cutting length of 51 mm, as short fiber B,
0.5 denier fineness made of polyethylene terephthalate (relative viscosity 1.38, melting point 257 ° C), cutting length 38m
m as the binder fiber, and the core is made of polyethylene terephthalate (relative viscosity 1.38, melting point 257)
° C), and the sheath portion is a copolymerized polyester having a terephthalic acid / isophthalic acid copolymerization molar ratio of 60/40 (relative viscosity 1.37;
(Softening point 110 ° C) core / sheath composite ratio 1/1 (weight ratio)
A conjugate fiber having a core-sheath type of 2 denier and a cut length of 51 mm was prepared.

The mixing ratio of the short fiber A and the binder fiber is 80/2.
0 (weight%) and passed through a fine carding machine to form a nonwoven web (layer A) with a basis weight of 600 g / m ² . Next, the short fiber B and the binder fiber were mixed at a mixing ratio of 80/20 (% by weight), passed through a fineness card machine, and weighed 200 g.
/ M ² of nonwoven web (layer B).

The laminate obtained by laminating the obtained layer A and layer B was sandwiched between a wire mesh together with a spacer having a thickness of 20 mm, and the thickness was regulated in a hot air circulating drier at 150 ° C.
Heat treated for 0 minutes, thickness 20mm, apparent density 0.0
4 g / cm ³ of the sound absorbing material of Example 1 was obtained.

Example 2 In Example 1, a short fiber having a denier of 13 denier was used as the short fiber A, and the core was made of polyethylene terephthalate (relative viscosity 1.38, melting point 257 ° C.) as a binder fiber.
The sheath portion is a copolymerized polyester obtained by copolymerizing ethylene terephthalate unit (A) / butylene terephthalate unit (B) [molar ratio 1/1] with ε-caprolactone (C), and ε-caprolactone is a total polyester [(A + B)
+ C] is a core-in-sheath type composed of a copolymerized polyester (relative viscosity 1.34, softening point 144 ° C.) blended at 20 mol% with respect to the total mole of the polyester and having a denier of 2 denier. Using a conjugate fiber having a cut length of 51 mm, a nonwoven web (layer A) having a basis weight of 400 g / m ² in which short fibers A and binder fibers were mixed at a mixing ratio of 70/30 (% by weight) was formed. Layer) also has a basis weight of 400 g / m ² ,
Example 1 except that the heat treatment was carried out in a hot air circulating dryer at a temperature of 200 ° C
In the same manner as in Example 1, a sound absorbing material of Example 2 was obtained.

Example 3 In Example 1, the basis weight of the nonwoven web (layer A) was 525.
g / m ^2, and the basis weight of the nonwoven web (layer B) is 75 g / m 2.
Similarly 20mm thick except for using ² as in Example 1 to obtain a sound-absorbing material of Example 3 of apparent density 0.03 g / cm ^3.

Example 4 In Example 1, a short fiber A having a fineness of 2 denier and a round fiber was used as the short fiber A, a short fiber B having a fineness of 1.25 denier and a short fiber having a triangular cross section was used. the basis weight of the layer) and 400 g / m ^2, except that the basis weight of the nonwoven web (B layer) was 400 g / m ² was obtained a sound-absorbing material of example 1 and example 4 in the same manner.

Example 5 In Example 1, the short fiber B and the binder fiber were mixed at a mixing ratio of 4
A sound absorbing material of Example 5 was obtained in the same manner as in Example 1 except that the cotton was mixed at 0/60 (% by weight).

Example 6 In Example 1, the basis weight of the nonwoven web (layer A) was 800
g / m ^2, and the basis weight of the nonwoven web (layer B) is 400 g / m ^2.
thickness except that the m ² in the same manner as in Example 1 30 mm,
The sound absorbing material of Example 6 having an apparent density of 0.04 g / cm ³ was obtained.

Comparative Example 1 The sound absorbing material of Comparative Example 1 having a thickness of 15 mm and an apparent density of 0.04 g / cm ^{3 was} prepared in the same manner as in Example 1 except that the nonwoven web (Layer B) was not laminated. I got

Comparative Example 2 In Example 1, the basis weight of the nonwoven web (layer A) was 800
g / m ^2, and a sound absorbing material of Comparative Example 2 having a thickness of 20 mm and an apparent density of 0.04 g / cm ³ was obtained in the same manner as in Example 1 except that the nonwoven web (layer B) was not laminated.

Comparative Example 3 In Example 1, the short fibers A / short fibers B / binder fibers were mixed at a rate of 60/10/30 (% by weight) to give a basis weight of 800.
A sound absorbing material of Comparative Example 3 was obtained in the same manner as in Example 1 except that a nonwoven web of g / m ² was used.

Comparative Example 4 In Example 1, the basis weight of the nonwoven web (layer B) was 120
A trial production of a sound absorbing material having a thickness of 30 mm and an apparent density of 0.04 g / cm ³ was attempted in the same manner as in Example 1 except that the nonwoven web (Layer A) was not laminated and the nonwoven web (Layer A) was set to 0 g / m ^2. Due to poor properties, a sound absorbing material could not be obtained.

Table 1 shows the results of measuring the normal incidence sound absorption coefficient of the sound absorbing materials comprising the fiber aggregates obtained in Examples 1 to 6 and Comparative Examples 1 to 3.

[0051]

[Table 1]

The sound-absorbing materials of Examples 1 to 6 of the present invention had a higher sound-absorbing effect than the sound-absorbing materials of Comparative Examples 1 and 2 each comprising a single-layer nonwoven web.

Further, the sound absorbing material of Example 5 and the sound absorbing material of Comparative Example 3 have short fibers with small fineness on the sound absorbing surface side even though the mixing ratio of the three types of short fibers as the sound absorbing material is the same. The sound absorbing material of Example 5 which was arranged in a concentrated manner was a sound absorbing material having a higher sound absorbing effect than the sound absorbing material of Comparative Example 3 in which only three kinds of short fibers were mixed.

[0054]

The sound-absorbing material comprising the fiber aggregate of the present invention is
Since the fibers with small fineness are arranged on the sound absorbing surface side, a high sound absorbing effect is exhibited. In addition, since the fiber having a large fineness has shape retention and rigidity, the sound absorbing material has a low density and can secure a certain thickness, the sound absorbing effect by the thickness is improved, and the light weight and the sound absorbing effect are high. It will be.

Therefore, the sound absorbing material made of the fiber aggregate of the present invention has the above-mentioned structure, and can exhibit a high sound absorbing effect even with a low weight, thereby reducing the weight and cost. It is possible to provide a sound-absorbing material suitable for a required automobile.

Claims (3)

[Claims] 1. A short fiber B having a denier of 2 denier or less and a fineness smaller than the short fiber A and a binder fiber on one side of a nonwoven web (layer A) comprising 2-15 denier short fibers A and binder fibers. The binder fiber has a binder component having a melting point or softening point lower than that of the short fibers A and B by at least 20 ° C. on at least the fiber surface. ,
A sound absorbing material, wherein constituent fibers are adhered to each other by melting a binder component, and the thickness of the fiber aggregate is 5 mm or more and the apparent density is 0.01 g / cm ³ or more. 2. The short fiber A and the short fiber B are made of polyethylene terephthalate, the binder fiber is polyethylene terephthalate in the core, and the copolymerization ratio (molar ratio) of terephthalic acid / isophthalic acid is 60/40 to 90/10 in the sheath. 2. The sound-absorbing material according to claim 1, wherein the sound-absorbing material is a core-sheath conjugate fiber in which a copolymerized polyester copolymerized in the above is disposed. 3. A core-sheath composite in which short fibers A and B are made of polyethylene terephthalate, binder fibers are polyethylene terephthalate in the core, and ε-caprolactone copolymer polyester having a crystal melting point of 100 ° C. or more in the sheath. The sound absorbing material according to claim 1, wherein the sound absorbing material is a fiber.