JPH10251956A - Sound-absorbing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sound-absorbing material having a high sound-absorbing effect even in a low METSUKE and suitable for automobiles by adhering staple fibers each having a flat cross-sectional shape through binder fibers having a low melting point binder component. SOLUTION: This sound-absorbing material comprises 90-50wt.% of main staple fibers each having a flat cross section having a flatness rate: (a-b)/a of 0.5-0.9 and 10-50wt.% of binder fibers having a binder component having a lower softening point by 20 deg.C or larger than that of the main staple fibers at least on the surfaces of the fibers. The binder component is melted to adhere the constituting fibers to each other. The adhered fiber mass has a thickness of >=5mm and an apparent density of >=0.01g/cm<3> .

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 comprising a fiber assembly. More specifically, the present invention relates to a sound absorbing material having a low weight and excellent sound absorbing performance, 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
In the sound absorbing material comprising a fiber aggregate having a fiber diameter of more than 1.5 denier according to the method disclosed in Japanese Patent No. 88951, it cannot be said that a sufficient sound absorbing effect can be obtained yet. I have to rely on it. 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 which solves the contradictory problems of a high sound absorbing effect and a reduction in weight and cost.

[0007]

Means for Solving the Problems The present inventors have made short fibers having a flat fiber cross section as a main constituent fiber, and bonded the constituent fibers to each other via a binder fiber having a binder component having a low softening point. It was found that a high sound absorbing effect was exhibited when the sound absorbing material of the fiber assembly was used, and the present invention was reached.

That is, according to the present invention, the main short fibers 90 to 50 whose cross-sectional shape is a flat cross section having a flatness of 0.5 to 0.9.
% By weight, and 10 to 50% by weight of a binder fiber having a binder component having a softening point lower than that of the main short fiber by at least 20 ° C. on the fiber surface, and the constituent fibers are bonded to each other by melting the binder component. The gist of the present invention is a sound absorbing material comprising an aggregate, wherein the thickness of the fiber aggregate is 5 mm or more and the apparent density is 0.01 g / cm ³ or more.

Flatness = (ab) / a (where a is the major axis in the fiber cross section, and b is the minor axis in the fiber cross section.)

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The cross-sectional shape of the main short fiber used in the present invention is a flat cross section having a flatness of 0.5 to 0.9. FIG. 1 shows a cross section of a fiber having a flat cross section, which is a main short fiber of the present invention. a is the long axis in the fiber cross section, b is the short axis in the fiber cross section, and the flattening ratio is flattening ratio = (ab) / a. However, if the flattening ratio is less than 0.5, the cross-sectional shape becomes similar to the round cross-section, so that the flat cross-section does not improve the sound absorbing effect. On the other hand, if the flatness exceeds 0.9, the short axis b must be lengthened rather than shortened in the nozzle processing, so the yarn bending due to the increase in the nozzle contact surface and the spinning tension increase. The resulting yarn breakage is not preferable because the operability is significantly impaired. For the above reason, the flatness of the main short fiber is preferably 0.7 to 0.8.

The main short fibers and the binder fibers used in the present invention are a polyester polymer, a polyamide polymer,
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), polycapramide (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.

Examples of the polyolefin polymer include aliphatic α-monoolefins having 2 to 18 carbon atoms, such as 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.

[0015] The fiber-forming thermoplastic polymer has the following properties:
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 fibers used in the present invention are 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 softening point lower than that of the main staple fiber by 20 ° C. or more on the fiber surface, and the binder component bonds the constituent fibers by heat melting. It is. The binder component needs to have a softening point lower than the main short fiber by 20 ° C. or more. The difference between the two is 20
It is not preferable that the temperature is lower than 0 ° C., since even the main short fibers may be softened and melted when the binder component is melted by heat.

The form of the binder fiber may be any form having at least a binder component on the fiber surface, 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 softening point lower than that of the polymer disposed in the core by 20 ° C. or more is disposed in the sheath is preferably used. The core-sheath type conjugate fiber is preferable because only the sheath part functions as a binder for adhering the constituent fibers to each other, and the core part maintains the form of the fiber, thereby contributing 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 the copolymerization ratio (molar ratio) of terephthalic acid / isophthalic acid is 60/40 to 90 in the sheath.
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, a polyester obtained by copolymerizing an ethylene terephthalate unit and / or a butylene terephthalate unit with an ε-caprolactone unit is suitable. Alternatively, it may be obtained by additionally copolymerizing isophthalic acid, naphthalene-2,6-dicarboxylic acid, adipic acid, sebacic acid, ethylene glycol, 1,6-hexanediol and the like. The proportion of the additional copolymer component is desirably 20 mol% or less based on the number of moles of the constituent components of the polyester. Further, the ε-caprolactone unit in the polyester may be either a random copolymer with other constituent units or a block copolymer.

The fineness of the main short fibers and the binder fibers used in the present invention is preferably 4 deniers or less. If the fineness of the main short fiber and the binder fiber exceeds 4 denier, the sound absorbing effect tends to be inferior, which is not preferable. The lower limit of the constituent fibers is not particularly limited, but is about 1 denier. If the fineness of the main staple fiber is less than 1 denier, spinning is actually difficult, and the flat cross section fiber tends to be inexpensive or rationally difficult to obtain.If the fineness of the binder fiber is less than 1 denier, There is a tendency that it is difficult to produce a core-sheath type conjugate fiber which is a preferred embodiment in the present invention. For the above reasons, the fineness of the main short fiber is preferably 2 to 3 denier, and the more preferable fineness of the binder fiber is 1 to 2 denier, more preferably 1.5 to 2 denier.

According to the present invention, there is provided a fiber assembly composed of a main short fiber and a binder fiber having a mixing ratio of 90/10 to 50/50% by weight. If the mixing ratio of the binder fibers is less than 10% by weight, the number of bonding points between the constituent fibers is reduced, and the rigidity and shape stability of the fiber aggregate are undesirably reduced.
On the other hand, when the mixing ratio of the binder fiber exceeds 50% by weight,
Since the ratio of the binder component melted during thermoforming increases, the sound absorbing effect of the fiber is impaired, which is not preferable. In consideration of sound absorption performance and form stability, the mixing ratio of the main short fiber and the binder fiber is 85/15 to 70/30.
% By weight is particularly preferred.

The thickness of the sound absorbing material is 5 mm or more, and
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 0.15 g / cm ^{3 in} consideration of the weight of the sound absorbing material. If it exceeds 0.15 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 0.08.
g / cm ^3, more preferably 0.02 to 0.1 g / cm ³ .
05 g / cm ³ .

[0025]

The sound-absorbing material comprising the fiber aggregate of the present invention uses fibers having a flat cross section as a main constituent fiber. It is presumed that the flat cross-section fiber has the same fineness and the cross-sectional shape has a lower bending stiffness than the round cross-section fiber, and is easy to convert vibration energy into heat energy. In comparison, it is considered that the sound absorbing effect is enhanced because the contact area with the air is increased.

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.

[0027]

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.

[0029]

(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 Perkin Elmer 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 main short fiber, a flat cross section fiber made of polyethylene terephthalate (relative viscosity: 1.38, melting point: 257 ° C.), fineness: 2 denier, cut length: 51 mm, and flatness: 0.72 was prepared. As the binder fiber, the core component was polyethylene terephthalate (relative viscosity 1.38, melting point 257)
° C), and a copolyester having a terephthalic acid / isophthalic acid copolymer molar ratio of 60/40 (relative viscosity 1.3).
7, a softening point of 110 ° C.) and a core-sheath composite fiber having a denier of 2 denier and a cut length of 51 mm were prepared at a core-sheath composite ratio of 1/1 (weight ratio). Mixing ratio of main short fiber and binder fiber 7
At 0/30 (wt%), pass through a fineness card machine to obtain a basis weight of 8
A web of 00 g / m ² was formed. Furthermore, the web was heat-treated in a hot-air circulating drier at 150 ° C. for 20 minutes while regulating the thickness by sandwiching the web between a wire mesh together with a spacer having a thickness of 20 mm to obtain a thickness of 20 mm and an apparent density of 0.04.
g / cm ³ of the sound absorbing material of Example 1 was obtained.

Example 2 In Example 1, the core part was polyethylene terephthalate (relative viscosity 1.38, melting point 257) as the binder fiber.
° C), and the sheath portion is converted to ε- by ethylene terephthalate unit (A) / butylene terephthalate unit (B) [molar ratio 1/1].
Caprolactone (C) is copolymerized polyester, and ε-caprolactone is a total polyester [(A +
B) + C] is a core / sheath type having a core / sheath composite ratio of 1/1 (weight ratio) composed of a copolymerized polyester (relative viscosity: 1.34, softening point: 144 ° C.) blended in an amount of 20 mol% with respect to the total mole of fineness. 2
Using a denier composite fiber with a cut length of 51 mm, 170 ° C
The sound absorbing material of Example 2 was obtained in the same manner as in Example 1 except that the heat treatment was performed in a hot air circulation dryer.

Example 3 A sound absorbing material of Example 3 was obtained in the same manner as in Example 1 except that the mixing ratio of the main short fiber and the binder fiber was 85/15 (% by weight).

Comparative Example 1 The procedure of Example 1 was repeated, except that the main short fibers having a round cross section were used, and the mixing ratio of the main short fibers and the binder fiber was 85/15 (% by weight). The sound absorbing material of Example 3 was 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 3 and Comparative Example 1.

[0039]

[Table 1]

The sound-absorbing materials of Examples 1 to 3 according to the present invention in which the fibers having a flat cross-sectional shape are mainly short fibers are compared with the sound-absorbing materials of Comparative Example 1 in which the fibers having a round cross-sectional shape are mainly short fibers. , A sound absorbing material having a high sound absorbing effect. Further, in Examples 1 to 3, Example 3 having a large mixing ratio of the main short fibers was used.
The sound absorbing material has the most excellent sound absorbing effect.

[0041]

The sound-absorbing material comprising the fiber aggregate of the present invention is
Since the constituent fibers have a flat cross section, a high sound absorbing effect can be exhibited even with a low basis weight. In addition, since the weight per unit area is low, it is possible to provide a sound-absorbing material suitable for an automobile requiring light weight and low cost.

[Brief description of the drawings]

FIG. 1 is a view showing a cross section of a fiber having a flat cross section, which is a main short fiber of the present invention.

[Explanation of symbols]

 a: major axis in fiber cross section b: minor axis in fiber cross section

Claims (4)

[Claims] 1. A fiber comprising at least 90 to 50% by weight of a main short fiber having a flat cross section having a flatness of 0.5 to 0.9 and a binder component having a softening point lower than that of the main short fiber by 20 ° C. or more. Binder fibers 10 to 50 on the surface
% By weight, and a fiber aggregate in which constituent fibers are adhered to each other by melting a binder component. The fiber aggregate has a thickness of 5 mm or more and an apparent density of 0.01 g / g.
A sound absorbing material having a size of at least cm ³ . Flatness = (ab) / a (where a is the major axis in the fiber cross section and b is the minor axis in the fiber cross section.) 2. The sound-absorbing material according to claim 1, wherein the fineness of the main short fibers and the binder fibers is 4 deniers or less. 3. 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 at a copolymerization ratio (molar ratio) of 60/40 to 90/10. 2. The sound-absorbing material according to claim 1, wherein the sound-absorbing material is a core-sheath type composite fiber provided with a copolymerized polyester. 4. A core-sheath type composite fiber 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. The sound absorbing material according to claim 1, wherein: