JP2010248666A - Sound-absorbing material and sound-absorbing composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound-absorbing material which has good flame retardancy and heat resistance, is thin and lightweight, and is excellent in a sound-absorbing performance; and to provide a sound-absorbing composite material. <P>SOLUTION: There is provided the sound-absorbing material which comprises aromatic polyamide nanofibers each having a diameter of 10-500 nm on a cross section orthogonal to the axis of the fiber and has a sound-absorbing rate of ≥60% at a frequency of 4,000 Hz. And there is provided the sound-absorbing composite material which is produced by laminating one or more layers comprising aromatic polyamide nanofibers each having a diameter of 10-500 nm on a cross section orthogonal to the axis of the fiber, to one or more fiber structure layers comprising fibers each having a diameter of 0.5-100 μm on a cross section orthogonal to the axis of the fiber, and has a sound-absorbing rate of ≥60% at a frequency of 4,000 Hz. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sound-absorbing material and a sound-absorbing composite material, and further relates to a sound-absorbing material suitable for vehicles, electrical products and the like that require flame retardancy and heat resistance.

  Conventionally, various sound absorbing materials have been used for vehicles, electrical products and the like. In order to respond to environmental problems and improve fuel efficiency, sound-absorbing materials for vehicles are lightweight and sound-absorbing materials with excellent sound-absorbing performance, and electrical appliances require thin and sound-absorbing materials to save space. Is growing.

For example, a nonwoven fabric having a basis weight of 30 to 200 g / m ² containing ultrafine fibers having a cross-sectional diameter of 6 μm or less and a short fiber nonwoven fabric having a cross-sectional diameter of 7 to 40 μm and a basis weight of 50 to 2000 g / m ² sound absorbing material, characterized in that it is integrated by entanglement on one side one side of (Patent Document 1) and in fineness 1.0~10dtex of surface density 100 to 500 g / ^{m 2} needle punched organic fiber nonwoven fabric, mainly fineness 1 A sound-absorbing material characterized in that a melt blown thermoplastic fiber nonwoven fabric having a surface density of 20 to 100 g / m ² at 0.0 dtex or less is laminated and further needle punched to have a total thickness of 2 to 30 mm (Patent Document 2) ) Has been proposed. However, in order to obtain sufficient sound absorption characteristics, the basis weight of the ultra-fine fiber nonwoven fabric having a large part of the sound absorption performance is required to be about 100 g / m ² , and it can be said that a thin and lightweight sound absorbing material has been obtained. Absent.

  In addition, the ultrafine fiber with improved sound absorption performance has a problem that it is easy to burn due to its high specific surface area. In particular, ultrafine fibers spun by the melt-blowing method are generally polypropylene, and are more likely to burn from the viewpoint of the material, and are applied for safety reasons in applications that are close to or in contact with heating elements such as vehicle engine rooms and motors. The current situation is difficult to do.

JP 2001-279567 A JP 2002-200747 A

  An object of the present invention is to provide a sound-absorbing material and a sound-absorbing composite material that have flame retardancy and heat resistance, are thin and lightweight, and have excellent sound-absorbing performance.

As a result of intensive studies by the present inventors, it has been found that the above problem can be solved by adopting the configuration described below.
That is, the present invention is a sound-absorbing material comprising aromatic polyamide nanofibers having a cross-sectional diameter of 10 to 500 nm perpendicular to the fiber axis and having a sound absorption coefficient of 60% or more at a frequency of 4000 Hz.

  In another aspect of the present invention, one or more nanofiber layers composed of aromatic polyamide nanofibers having a cross-sectional diameter of 10 to 500 nm perpendicular to the fiber axis, and a cross-sectional diameter of 0.5 to 100 μm perpendicular to the fiber axis. It is a sound-absorbing composite material in which one or more fiber structure layers made of fibers are laminated and the sound absorption coefficient at a frequency of 4000 Hz is 60% or more.

In the above sound-absorbing material and sound-absorbing composite material, the aromatic polyamide is an aromatic polyamide different from the main structural unit of the repeating structure in the aromatic polyamide skeleton containing the repeating structural unit represented by the following formula (1). The diamine component or the aromatic dicarboxylic acid halide component is preferably an aromatic polyamide copolymerized so as to be 1 to 10 mol% based on the total amount of the repeating structural units of the aromatic polyamide as the third component.
-(NH-Ar1-NH-CO-Ar1-CO) -... Formula (1)
Here, Ar1 is a divalent aromatic group having a bonding group other than in the meta-coordinate or parallel axis direction.

  According to the present invention, since the superiority of nanofibers can be fully expressed, even in a thin and lightweight fiber structure, high sound absorption performance can be obtained, and furthermore, a wholly aromatic aramid polymer excellent in flame retardancy and heat resistance By using the nanofiber made of, a sound-absorbing material that can be used even in a high-temperature atmosphere where it was difficult to apply ultrafine fibers is provided.

  The sound-absorbing material in the present invention is characterized in that the sound absorption coefficient at a frequency of 4000 Hz made of aromatic polyamide nanofibers having a cross-sectional diameter of 10 to 500 nm perpendicular to the fiber axis is 60% or more.

The nanofiber constituting the sound absorbing material needs to have a cross-sectional diameter of 10 to 500 nm, preferably 50 to 300 nm. If the cross-sectional diameter is less than 10 nm, the strength obtained is significantly reduced, so that the nanofiber is easily damaged. On the other hand, if the cross-sectional diameter of the nanofiber exceeds 500 nm, various characteristics peculiar to the nanometer order, for example, high sound absorption characteristics Becomes difficult to be expressed.
The nanofiber weight per unit area is preferably 0.1 to 20 g / m ² from the viewpoint of sound absorption performance, thickness, and weight.

  The sound absorbing material may be nanofibers alone, and fibers other than aromatic polyamide nanofibers may be included in order to improve handleability. The cross-sectional diameter of the fiber perpendicular to the fiber axis is preferably 0.5 to 100 μm.

  The sound-absorbing composite material of the present invention includes one or more nanofiber layers composed of the above aromatic polyamide nanofibers and one or more fiber structure layers composed of fibers having a cross-sectional diameter of 0.5 to 100 μm perpendicular to the fiber axis. And the sound absorption coefficient at a frequency of 4000 Hz is 60% or more. The fiber structure may be a woven fabric, a knitted fabric, a nonwoven fabric, or any combination thereof.

40-2000 g / m < ² > is preferable and 40-1000 g / m < ² > is more preferable as content of the fiber (weight basis conversion) contained in the said sound-absorbing material, and the fabric weight of the fiber structure used for the said sound-absorbing composite material. On the other hand, if the fiber content (basis weight conversion) and the basis weight of the fiber structure are less than 40 g / m ² , the handleability is not improved so much, and if it exceeds 2000 g / m ² , the weight can be reduced. The flexibility is also reduced and the cost is increased.

  Further, as described above, the cross-sectional diameter of the fiber contained in the sound absorbing material and the fiber constituting the fiber structure used in the sound absorbing composite material perpendicular to the fiber axis is 0.5 to 100 μm, preferably 0.5 to 50 μm. When the cross-sectional diameter is less than 0.5 μm, the handleability is not improved so much, while when it exceeds 100 μm, the flexibility is lowered.

Fibers contained in the sound absorbing material and fibers constituting the fiber structure used in the sound absorbing composite material are not particularly limited, but are cellulose fiber, protein fiber, polyethylene, polypropylene, polyethylene terephthalate, polyacrylonitrile. Nylon type such as nylon 6 and nylon 66, organic fiber such as aromatic polyamide, inorganic fiber such as glass fiber and carbon fiber, and metal fiber such as steel fiber can be used.
The sound-absorbing material and the sound-absorbing composite material may be subjected to heat treatment, pressure treatment, and heat-pressure treatment by calendaring, embossing, or the like.

  The sound absorbing material of the present invention can be manufactured, for example, by the following method. One method is preferably a method of forming nanofibers by spraying an aromatic polyamide solution on a fabric, film, paper, etc., which is easy to peel off the nanofiber layer later by applying a high voltage. It can be illustrated. Further, the cross-sectional diameter of the obtained nanofiber depends on the applied voltage, the solution concentration, the spray scattering distance, and the like, and can be set to an arbitrary cross-sectional diameter by adjusting these conditions. As the solvent, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide and the like can be used.

  As conditions for the electrospinning, the concentration is 1 to 16%, the voltage is 5.0 to 70 kV, the spinning distance is 5.0 to 50 cm, and the voltage per unit distance is 0.5 to 7.0 kv / cm. Preferably there is.

  Specifically, an aramid having the aforementioned cross-sectional diameter is prepared by preparing a polymer solution in which an aromatic polyamide polymer and a solvent are dissolved in a weight ratio of 1:99 to 16:84 and performing under a voltage of 5 to 70 kV. Nanofibers can be made.

  Examples of the spinning solution supply include a method of extruding from a nozzle and a base, and a method of supplying the spinning solution by attaching it to a disk or drum immersed in the spinning solution so that it becomes a required amount and continuously rotating it. When supplying from a nozzle or a nozzle | cap | die, since the internal diameter of a discharge part has no correlation with the cross-sectional diameter of nanofiber, there is no limitation.

  Some materials such as polyacrylonitrile, polyvinyl alcohol, nylon 6, and polyurethane can be easily molded, but they are not preferable because they are inferior in flame retardancy and heat resistance and are difficult to use in a high temperature atmosphere for a long time.

In the aromatic polyamide nanofiber constituting the sound absorbing material, the aromatic polyamide is an aromatic polyamide different from the main structural unit of the repeating structure in the aromatic polyamide skeleton including the repeating structural unit represented by the following formula (1). The diamine component or the aromatic dicarboxylic acid halide component is preferably an aromatic polyamide copolymerized so as to be 1 to 10 mol% based on the total amount of the repeating structural units of the aromatic polyamide as the third component.
-(NH-Ar1-NH-CO-Ar1-CO) -... Formula (1)
Here, Ar1 is a divalent aromatic group having a bonding group other than in the meta-coordinate or parallel axis direction.

More preferably, the aromatic diamine serving as the third component is preferably the formula (2) or (3), and the aromatic dicarboxylic acid halide is preferably the formula (4) or (5).
H ₂ N—Ar ₂ —NH ₂ Formula (2)
_{H 2 N-Ar2-Y-} Ar2-NH 2 ··· formula (3)
XOC-Ar3-COX Formula (4)
XOC-Ar3-Y-Ar3-COX Formula (5)
Here, Ar2 is a divalent aromatic group different from Ar1, Ar3 is a divalent aromatic group different from Ar1, Y is at least one atom selected from the group consisting of an oxygen atom, a sulfur atom, and an alkylene group, or It is a functional group, and X represents a halogen atom.

  By copolymerizing the third component, the molecular chain structure is disturbed, the crystallinity is lowered, and the stability of the spinning solution is improved. Therefore, the nanofibers formed from the spinning solution are prevented from being formed into a film. Therefore, when used as a sound absorbing material, the reflection of sound waves is reduced and the sound absorbing performance is improved.

  If the content of the third component is less than 1 mol%, gelation occurs in the spinning solution, which is not preferable. If the content exceeds 10 mol%, the viscosity of the spinning solution increases, and nanofibers having a target cross-sectional diameter are not obtained. It is difficult to obtain and is not preferable.

  In addition to the above method, there is a method of adding an alkali metal salt and / or an alkaline earth metal salt as a method for improving the stabilization of the spinning solution, but the salt remains in the nanofiber, and the residual salt Leakage may cause corrosion of members adjacent to the composite fiber structure, which is not preferable.

  The sound-absorbing material containing fibers other than the aromatic polyamide nanofibers described above, when forming nanofibers by electrospinning, simultaneously spinning the other fibers by a spunbond method, a melt blow method, a flash spinning method, It can be manufactured by mixing the other fibers in the electrospinning space by wind or the like and mixing them in the nanofibers.

  In addition, as a method for producing a sound-absorbing composite material in which a nanofiber layer and a fiber structure layer are laminated, a method of laminating nanofibers directly on the fiber structure when spinning nanofibers by electrospinning is preferable. Further, as described above, a nanofiber layer may be separately prepared and later laminated on the fiber structure.

  Furthermore, in this invention, after laminating | stacking a nanofiber layer and a fiber structure layer, these can be firmly adhere | attached by giving heat processing, a pressurization heat processing, etc. Moreover, when laminating | stacking a nanofiber layer and a fiber structure, an adhesive agent may be apply | coated to one side of the fiber structure on which a nanofiber layer is laminated | stacked, and these may be adhered more firmly. By performing such an adhesion process, the adhesion between the nanofiber layer and the fiber structure is improved, and a sound-absorbing composite material with more excellent processability and handleability can be obtained.

  The adhesive is not particularly limited, but may be an organic adhesive such as an acrylic resin adhesive, a urethane resin adhesive, an epoxy resin emulsion adhesive, a vinyl acetate resin emulsion adhesive, or a silicone adhesive. Often, an inorganic adhesive such as a silica-based adhesive is used.

  The heat treatment method is not particularly limited, and examples thereof include heat treatment such as through-air processing, pressure heat treatment such as calendar processing and embossing. In the pressurization heat treatment, a processing temperature of 30 to 350 ° C. and a linear pressure of 30 to 300 kg / cm can be preferably employed.

  The nanofiber layer and the fiber structure layer may be obtained by laminating a plurality of nanofiber structures and fiber structures. Further, a fiber structure layer may be further provided on the nanofiber layer laminated on the fiber structure layer, and the nanofiber layer may be sandwiched between the fiber structure layers.

  The sound-absorbing material and sound-absorbing composite material of the present invention obtained as described above have a high sound-absorbing performance of 60% or more at a frequency of 4000 Hz while being thin and light, and further have an excellent aroma and flame resistance. By using the group aramid nanofiber, it can be used even in a high temperature atmosphere.

Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited by the following examples. In addition, each characteristic value in an Example was measured with the following method.
(1) Section diameter About 100 nanofibers sampled arbitrarily, it measured with the scanning electron microscope JSM6330F (made by JEOL), and calculated | required the average value of section diameter. The measurement was performed at a magnification of 3,000 times for the upper layer and the lower layer, and 30,000 times for the middle layer.
(2) Weight per unit area The nanofiber layer and the fiber structure were sampled in a 15 cm square, the mass was measured, and the mass per 1 m ² was converted into the basis weight. In addition, when the nanofibers are directly laminated on the fiber structure, similarly, sampling at 15 cm square, measuring the mass of the fiber structure and the composite fiber structure after the nanofiber lamination, calculating the difference between the two, The mass per 1 m ² was converted into mass per unit area.
(3) Sound absorption rate It measured according to the transfer function method defined in ISO 10534-2 (measurement of sound absorption rate and impedance of an acoustic-impedance tube).

[Example 1]
The aromatic polyamide polymer of the present invention was produced by the interfacial polymerization method according to the method described in Japanese Patent Publication No. 47-10863 as follows.
25.25 g (100 mol%) of isophthalic acid dichloride was dissolved in 125 ml of tetrahydrofuran having a water content of 2 mg / 100 ml and cooled to −25 ° C. While stirring this, 13.52 g (100 mol%) of metaphenylenediamine was added over about 15 minutes as a trickle of a solution obtained by dissolving 125 ml of the above tetrahydrofuran to prepare a white emulsion (A). Separately, 13.25 g of anhydrous sodium carbonate was dissolved in 250 ml of water at room temperature, and this was cooled to 5 ° C. with stirring to precipitate sodium carbonate hydrate crystals to prepare a dispersion (B). The emulsion (A) and dispersion (B) were mixed vigorously. After further mixing for 2 minutes, 200 ml of water was added for dilution, and the resulting polymer was precipitated as a white powder. Filtration, washing with water and drying were carried out from the polymerization completed system to obtain the desired polymer.

Electrospinning produced nanofibers according to the method described in JP-A-2006-336173. The obtained polymer is dissolved in N, N-dimethylacetamide so as to be 10% by weight, electrospun is performed by applying an electric field so as to be 1 kV / cm, and nanofibers are laminated on the conductive polyolefin film. Furthermore, this was peeled from the conductive polyolefin film to obtain a sound-absorbing material consisting only of the nanofiber layer. The basis weight of the obtained sound absorbing material was 5 g / m ² . The results are shown in Table 1.
The obtained sound absorbing material was attached to the inside of the exterior sound insulation resin cover of a commercially available vacuum cleaner, and it was confirmed that the noise was reduced as compared with Comparative Example 1. Moreover, the deterioration by the heat | fever of nanofiber was not recognized.

[Example 2]
Nanofibers in the same manner as in Example 1 except that 25.25 g (100 mol%) of isophthalic acid dichloride and 25.13 g (99 mol%) of isophthalic acid dichloride and 0.25 g (1 mol%) of terephthalic acid dichloride were used. A sound absorbing material consisting only of layers was obtained. The results are shown in Table 1.
Moreover, although the obtained sound-absorbing material was attached to a vacuum cleaner in the same manner as in Example 1 and the noise was evaluated, it was confirmed that the noise was lower than that in Comparative Example 1. Moreover, the deterioration by the heat | fever of nanofiber was not recognized.

[Example 3]
In place of the conductive polyolefin film, a polyethylene terephthalate nonwoven fabric (Japanese nonwoven fabric bonnip) having a cross-sectional diameter of 24.1 μm, a basis weight of 300 g / m ² and a thickness of 1.5 cm was used. Nanofibers were laminated to obtain a laminate. At this time, the basis weight of the nanofiber layer was changed to 0.5 g / m ² . Thereafter, the obtained laminate was calendered at a temperature of 150 ° C., a linear pressure of 50 kg / cm, a spacer of 1 cm, and a roll speed of 1 m / min to obtain a sound-absorbing composite material comprising a nanofiber layer and a fiber structure layer. . The results are shown in Table 1.
Moreover, although the obtained sound-absorbing material was attached to a vacuum cleaner in the same manner as in Example 1 and the noise was evaluated, it was confirmed that the noise was lower than that in Comparative Example 1. Moreover, the deterioration by the heat | fever of nanofiber was not recognized.

[Example 4]
In place of the conductive polyolefin film, a polyethylene terephthalate nonwoven fabric (Japanese nonwoven fabric bonnip) having a cross-sectional diameter of 24.1 μm, a basis weight of 300 g / m ² and a thickness of 1.5 cm was used. Nanofibers were laminated to obtain a laminate. At this time, the basis weight of the nanofiber layer was changed to 0.5 g / m ² . Thereafter, the obtained laminate was calendered at a temperature of 150 ° C., 50 kg / cm, a spacer of 1 cm, and a roll speed of 1 m / min to obtain a sound-absorbing composite material comprising a nanofiber layer and a fiber structure layer. The results are shown in Table 1.
Moreover, although the obtained sound-absorbing material was attached to a vacuum cleaner in the same manner as in Example 1 and the noise was evaluated, it was confirmed that the noise was lower than that in Comparative Example 1. Moreover, the deterioration by the heat | fever of nanofiber was not recognized.

[Example 5]
A sound-absorbing composite material comprising a nanofiber layer and a fiber structure layer was obtained in the same manner as in Example 4 except that the nanofiber weight per unit area was changed to 15 g / m ² . The results are shown in Table 1.
Moreover, although the obtained sound-absorbing material was attached to a vacuum cleaner in the same manner as in Example 1 and the noise was evaluated, it was confirmed that the noise was lower than that in Comparative Example 1. Moreover, the deterioration by the heat | fever of nanofiber was not recognized.

[Example 6]
A sound-absorbing composite material comprising a nanofiber layer and a fiber structure layer was obtained in the same manner as in Example 4 except that the aromatic polyamide polymer was dissolved in N, N-dimethylacetamide so as to be 13%. The results are shown in Table 1.
Moreover, although the obtained sound-absorbing material was attached to a vacuum cleaner in the same manner as in Example 1 and the noise was evaluated, it was confirmed that the noise was lower than that in Comparative Example 1. Moreover, the deterioration by the heat | fever of nanofiber was not recognized.

[Example 7]
A nanofiber layer and a fiber structure layer are formed in the same manner as in Example 4 except that the nonwoven fabric on which the nanofibers are laminated is changed to a polyethylene terephthalate nonwoven fabric having a cross-sectional diameter of 15.5 μm, a basis weight of 80 g / m ² , and a thickness of 1 cm. A sound absorbing composite material was obtained. The results are shown in Table 1.
Moreover, although the obtained sound-absorbing material was attached to a vacuum cleaner in the same manner as in Example 1 and the noise was evaluated, it was confirmed that the noise was lower than that in Comparative Example 1. Moreover, the deterioration by the heat | fever of nanofiber was not recognized.

[Comparative Example 1]
A sound absorbing material was obtained in the same manner as in Example 3 except that the nanofibers were not laminated. The results are shown in Table 1.
Further, the obtained sound absorbing material was attached to a vacuum cleaner in the same manner as in Example 1, and the noise was evaluated. Based on this, the noise in Examples 1 to 5 was compared.

[Comparative Example 2]
Absorbing sound in the same manner as in Example 3 except that a polymer solution in which Kuraray polyvinyl alcohol was dissolved in water at a weight ratio of 7:93 was used instead of the wholly aromatic polyamide polymer solution. A composite material was obtained. After the heat and pressure treatment, the nanofibers could not be confirmed when observed with an operation electron microscope, and thus the evaluation was not performed.

  The sound-absorbing material and sound-absorbing composite material of the present invention have flame retardancy and heat resistance, are thin and lightweight, and have excellent sound-absorbing performance, so that they can be suitably used for vehicles, electrical products and the like.

Claims (7)

  A sound-absorbing material comprising an aromatic polyamide nanofiber having a cross-sectional diameter of 10 to 500 nm perpendicular to the fiber axis and having a sound absorption coefficient of 60% or more at a frequency of 4000 Hz. In the aromatic polyamide skeleton containing the repeating structural unit represented by the following formula (1), the aromatic polyamide contains an aromatic diamine component or an aromatic dicarboxylic acid halide component different from the main structural unit of the repeating structure. The sound-absorbing material according to claim 1, wherein the third component is an aromatic polyamide copolymerized so as to be 1 to 10 mol% with respect to the total amount of repeating structural units of the aromatic polyamide.
-(NH-Ar1-NH-CO-Ar1-CO) -... Formula (1)
Here, Ar1 is a divalent aromatic group having a bonding group other than in the meta-coordinate or parallel axis direction. The sound absorbing material according to claim 1 or 2, wherein the aromatic diamine as the third component is represented by the formula (2) or (3), and the aromatic dicarboxylic acid halide is represented by the formula (4) or (5).
H ₂ N—Ar ₂ —NH ₂ Formula (2)
_{H 2 N-Ar2-Y-} Ar2-NH 2 ··· formula (3)
XOC-Ar3-COX Formula (4)
XOC-Ar3-Y-Ar3-COX Formula (5)
Here, Ar2 is a divalent aromatic group different from Ar1, Ar3 is a divalent aromatic group different from Ar1, Y is at least one atom selected from the group consisting of an oxygen atom, a sulfur atom, and an alkylene group, or It is a functional group, and X represents a halogen atom.   The sound-absorbing material according to any one of claims 1 to 3, wherein the repeating structural unit of the aromatic polyamide is metaphenylene isophthalamide.   The sound-absorbing material according to any one of claims 1 to 4, comprising a fiber having a cross-sectional diameter orthogonal to the fiber axis of 0.5 to 100 µm.   One or more nanofiber layers made of aromatic polyamide nanofibers having a cross-sectional diameter of 10 to 500 nm perpendicular to the fiber axis, and one or more layers of fibers made of fibers having a cross-sectional diameter of 0.5 to 100 μm perpendicular to the fiber axis A sound-absorbing composite material obtained by laminating a structure layer and having a sound absorption coefficient of a frequency of 4000 Hz of 60% or more.   The sound-absorbing composite material according to claim 6, wherein the fiber structure layer is made of any one of a fabric woven fabric, a knitted fabric, and a non-woven fabric, or a combination thereof.