JP4869358B2 - Method for manufacturing diaphragm for electroacoustic transducer and diaphragm for electroacoustic transducer - Google Patents

Description

【Technical field】
[0001]
In the electroacoustic transducer diaphragm using carbon nanotubes as a matrix resin reinforcing material, the present invention performs surface treatment of carbon nanotubes, imparts chemical bonds with the matrix resin, and improves elastic modulus and tensile strength. The present invention relates to a method for manufacturing a diaphragm for an electroacoustic transducer having improved sound quality and durability, and a diaphragm for an electroacoustic transducer manufactured by the manufacturing method.
[Background]
[0002]
As a molding material for a diaphragm for an electroacoustic transducer, there is a composite material in which a matrix resin is reinforced with a powder such as high elastic modulus carbon fiber or mica.
However, since the size of the powder of high elastic modulus carbon fiber or mica is in the unit of μm, a sufficient composite effect cannot be obtained.
In contrast, carbon nanotubes have a size as small as nm units, and the contact area with the matrix resin is remarkably increased, so that dispersibility and interfacial adhesion are increased, and the aspect ratio is remarkably increased. Therefore, there is one in which a diaphragm for an electroacoustic transducer is formed from a composite material in which a matrix resin is reinforced with carbon nanotubes.
Thus, when carbon nanotubes are used as a matrix resin reinforcing agent, a diaphragm for an electroacoustic transducer having light weight, high elasticity, high internal loss, and excellent moldability, dimensional stability, heat resistance, etc. is obtained. be able to.
[Patent Document 1]
JP 2003-319488 A
[0003]
However, since the surface of the carbon nanotube is covered with a chemically stable sp2 bond, it is not possible to obtain a sufficient bonding force simply by adding an auxiliary agent for bonding the matrix resin and the carbon nanotube during kneading. There was a problem that desired elastic modulus and tensile strength could not be obtained.
The present invention has been proposed to solve the above-mentioned problems. The object of the present invention is to perform a surface treatment on the carbon nanotubes, to make the bonding force between the matrix resin and the carbon nanotubes sufficient, the elastic modulus, An object of the present invention is to provide a method for manufacturing a diaphragm for an electroacoustic transducer that has improved tensile strength, increased high-frequency limit frequency, and reduced distortion, and a diaphragm for the electroacoustic transducer.
DISCLOSURE OF THE INVENTION To achieve the above object, the method for producing a diaphragm for an electroacoustic transducer of the present invention is a surface treatment for chemically imparting a compound capable of improving affinity with a matrix resin to a surface by a covalent bond. It is characterized in that it is formed of a composite material obtained by reinforcing matrix resin with carbon nanotubes. The chemical bond refers to a bond such as a covalent bond or an ionic bond between the matrix resin and the carbon nanotube interface.
In the present invention, as the surface treatment, an aluminum-based coupling agent compound is chemically covalently bonded to the surface of the carbon nanotubes to form an organic film, and the matrix resin is formed from the surface-treated carbon nanotubes. It is characterized by being molded from a reinforced composite material.
Specifically, the carbon nanotube which heated the solution which added the aluminum type coupling agent with respect to hexane, added the carbon nanotube to this solution, stirred while refluxing the hexane, dried the hexane, and carried out the coupling process. Is molded by a composite material reinforced by kneading with the matrix resin.
Further, as another surface treatment, a functional group is added as a compound to the surface of the carbon nanotube, and a diaphragm for an electroacoustic transducer is formed by a composite material in which the matrix resin is reinforced with the surface-treated carbon nanotube, The carbon nanotube has a chemical covalent bond with the matrix resin.
In this case, the functional group consists of an amino group.
The modification of the amino group on the surface of the carbon nanotube is performed by adding carbon nanotubes to aqua regia and heating, filtering this solution through filter paper, heating and drying the carbon nanotubes remaining on the filter paper, After adding ultrasonic waves to triethylenetetramine and heating, the solution is filtered through a filter paper, the carbon nanotubes remaining on the filter paper are dried, and the surface treatment of the carbon nanotubes is performed. A diaphragm for an electroacoustic transducer is formed of a composite material in which the matrix resin is reinforced with the carbon nanotubes that have been surface-treated.
That is, in the electroacoustic transducer diaphragm of the present invention, an organic film is formed by chemically covalently bonding an aluminum coupling agent compound on the surface of the carbon nanotube, or the compound is formed on the surface of the carbon nanotube. As a functional group, the rigid carbon nanotube has a chemical covalent bond with the matrix resin. As a result, since the carbon nanotubes restrain the matrix resin, the elastic modulus and tensile strength were improved. Restraining the matrix resin means suppressing the mobility of the molecular chain of the matrix resin.
The diaphragm for electroacoustic transducers of the present invention has a surface treatment on the carbon nanotubes and has strengthened the chemical covalent bond with the matrix resin, so that the elastic modulus is improved. The critical frequency increased, distortion decreased, and sound quality improved. Moreover, the diaphragm for electroacoustic transducers of the present invention has improved tensile strength, thereby improving durability.
[Brief description of the drawings]
FIG. 1 shows an electron micrograph of a carbon nanotube according to Example 1 of the present invention, in which an aluminum-based coupling agent compound is chemically covalently bonded to the surface to form an organic film.
2 (a) and 2 (b) are explanatory views of the manufacturing process of the diaphragm by the injection molding machine.
FIG. 3 is a longitudinal sectional view of the produced electroacoustic transducer diaphragm.
FIG. 4 shows an electron micrograph of the carbon nanotube before the amino group is bonded.
FIG. 5 shows an electron micrograph of carbon nanotubes having amino groups bonded to the surface according to Example 2 of the present invention.
FIG. 6 shows the frequency characteristics with respect to the sound pressure in the conventional example and Example 2 of the present invention.
Explanation of symbols [0006]
DESCRIPTION OF SYMBOLS 1 Movable side metal mold | die 2 Fixed side metal mold | die 3 Mold 4 Nozzle of injection molding machine 5 Molding material 6 Diaphragm A Frequency characteristic of this invention product B Frequency characteristic of conventional product [Best Mode for Carrying Out the Invention]
[0007]
Carbon nanotubes having a diameter of 0.4 to 500 nm and a length of 0.06 to 200 μm were used. The reason why the direct system is 0.4 nm or more is that it is difficult to produce a carbon nanotube smaller than that. Further, the reason why the thickness is set to 500 nm or less is that if it is larger than this, it will be out of the desired physical property value of the diaphragm. Moreover, it is because it is difficult to manufacture if the length is 0.06 μm or less. The reason why the thickness is 200 μm or less is that if it is more than that, the desired physical property value of the diaphragm is not satisfied.
Examples of the matrix resin to be used include polypropylene (trade name: J108M, manufactured by Mitsui Chemicals, Inc.).
Other examples include polystyrene-saturated thermoplastic elastomers [styrene / ethylene / butylene / styrene block copolymer (SEBS), functionalized SEBS, styrene / ethylene / propylene / styrene block copolymer, random hydrogenated styrene / Butadiene polymer, etc.), ethylene / ethyl acrylate / maleic anhydride terpolymer, ethylene-modified α-olefin copolymer, modified polyolefin, etc., and these resins have relatively high adhesion to carbon nanotubes. good. Other than these may be used.
The surface treatment of carbon nanotubes was performed as follows.
[Example 1]
[0008]
A preferred embodiment of the surface treatment of carbon nanotubes with an aluminum coupling agent is as follows.
To 1 L (liter) of hexane, 1 g of an aluminum coupling agent (trade name: Plenact AL-M, manufactured by Ajinomoto Fine Techno Co., Ltd.) was added to prepare a dispersion solution. This solution was heated to 90 ° C., 100 g of carbon nanotubes (trade name VGCF, manufactured by Showa Denko KK) were added, and the mixture was stirred for 20 minutes while refluxing hexane.
Hexane was dried at 90 ° C. and subjected to a coupling treatment to treat the carbon nanotubes.
That is, in Example 1, an aluminum-based film was formed by chemically bonding (covalently bonding) an aluminum-based coupling agent compound to the surface of the carbon nanotubes by the above treatment.
FIG. 1 is an electron micrograph of a carbon nanotube according to Example 1 in which the above compound is chemically bonded to the surface. This organic film improves the affinity with the matrix resin, makes the carbon nanotubes easily wetted with the matrix resin, and at the same time increases the adhesion strength with the matrix resin.
Surface-treated carbon nanotubes and polypropylene (trade name J108M, manufactured by Mitsui Chemicals, Inc.) were sufficiently kneaded through a well-structured twin-screw kneader to produce a molding material.
Next, as shown in FIG. 2A, the nozzle 4 of the injection molding machine is applied into the cavity of the mold 3 composed of the movable mold 1 and the fixed mold 2 as shown in FIG. In addition, it is only necessary to take out the electroacoustic transducer diaphragm produced by filling the molding material 5 into the inside and performing injection molding and opening the mold after a predetermined time has elapsed. FIG. 3 is a schematic sectional view of the produced electroacoustic transducer diaphragm.
[Example 2]
[0009]
A preferred embodiment of the surface treatment by the amino group modification on the carbon nanotube surface is as follows.
1 g of the same carbon nanotube as in Example 1 was added to aqua regia (sulfuric acid: nitric acid = 3: 1) and heated at 105 ° C. for 1 hour.
This solution was filtered, and the carbon nanotubes remaining on the filter paper were dried at 80 ° C. for 12 hours.
To 400 mL of xylene, 4 g of the treated carbon nanotubes were added, 4 mL of triethylenetetramine was added, and after ultrasonic treatment for 10 minutes, heating was performed at 120 ° C. for 2 hours. This solution was filtered, and the carbon nanotubes remaining on the filter paper were dried at 80 ° C. for 12 hours.
It was confirmed by Raman spectroscopic analysis and infrared spectrophotometric analysis that the obtained carbon nanotube had an amino group bonded to the surface by a covalent bond.
This amino group is a functional group. The functional group is an atomic group having polarity such as an amino group, a hydroxyl group, or a carboxyl group. In the present invention, by attaching a functional group consisting of an amino group to the surface of the carbon nanotube by a chemical reaction as described above, the affinity for the matrix resin is improved, and the carbon nanotube is easily wetted by the matrix resin. At the same time, the adhesive strength with the matrix resin is increased.
FIG. 4 is an electron micrograph of carbon nanotubes before (non-treated) bonding of amino groups, and FIG. 5 is an electron micrograph showing a state in which amino groups are bonded to the surface of the carbon nanotubes.
As apparent from FIG. 5, the surface of the treated carbon nanotube is modified with an amino group, so that the outer diameter is increased correspondingly, and this amino group improves the wettability with respect to the matrix resin, and the matrix resin. The bond strength with the is also increased.
The amino nanotube-modified carbon nanotubes are kneaded with the same polypropylene as in Example 1, the carbon nanotubes are firmly bonded to the matrix resin, and the obtained pellets are similarly injection-molded to obtain a diaphragm for an electroacoustic transducer. Produced.
A speaker was assembled using this diaphragm for electroacoustic transducers, and the frequency characteristics were measured. As a result, the high frequency limit frequency increased due to the improvement of the elastic modulus, the distortion decreased, and good sound quality was obtained.
The diaphragms for electroacoustic transducers produced according to Examples 1 and 2 have the advantage that the strength increases and the durability is improved by increasing the bonding force between the matrix resin and the carbon nanotubes. In addition, the binding force between the matrix resin and the carbon nanotubes increases, so that the binding force on the matrix resin increases and the elastic modulus improves.
In FIG. 6, A shows the frequency characteristics of the product of the present invention according to the second embodiment, and B shows the characteristics of a diaphragm formed by injection molding pellets obtained by kneading carbon nanotubes not modified with amino groups in a matrix resin. The same characteristics can be obtained with a speaker using the electroacoustic transducer diaphragm according to the first embodiment.
In addition, this invention is not limited to the said Example, A various change is possible in the range which does not deviate from the mind of this invention. For example, in the above embodiment, polypropylene is used as the synthetic resin. However, other examples may be used, and in the second embodiment, an amino group is used as a functional group. However, other functional groups may be used. Moreover, although the example which produces a diaphragm by injection molding was demonstrated, it is also possible to produce by extrusion molding. Furthermore, the diaphragm shape is not limited to a conical shape, but may be a flat plate shape or other shapes.
[Industrial applicability]
[0010]
The diaphragm for an electroacoustic transducer of the present invention is incorporated in an acoustic device such as a speaker or a microphone. A voice coil is coupled to the diaphragm, and when a voice signal is applied to the voice coil, the diaphragm vibrates and emits sound waves.

Claims (2)

Forming an organic coating on the surface of carbon nanotubes by chemically bonding an aluminum-based coupling agent compound in order to chemically and covalently attach a compound that can improve the affinity with the matrix resin to the surface A method of manufacturing a diaphragm for an electroacoustic transducer in which a diaphragm is formed from a composite material in which the surface-treated carbon nanotubes are reinforced with a matrix resin, wherein a solution obtained by adding an aluminum coupling agent to hexane is heated. Then, carbon nanotubes are added to the solution, and the hexane is refluxed and stirred, and then the diaphragm is formed from a composite material obtained by kneading the carbon nanotubes, which is dried and coupled, with the matrix resin. The manufacturing method of the diaphragm for electroacoustic transducers. In order to chemically impart a compound capable of improving the affinity with the matrix resin to the surface by a covalent bond, a functional group consisting of an amino group is added to the surface of the carbon nanotube as the compound, and the surface-treated carbon nanotube A method for manufacturing a diaphragm for an electroacoustic transducer, wherein the matrix resin is reinforced and a diaphragm is formed from a composite material having a chemical covalent bond between the carbon nanotube and the matrix resin, the surface of the carbon nanotube To modify the amino group, carbon nanotubes are added to aqua regia and heated, the solution is filtered through filter paper, the carbon nanotubes remaining on the filter paper are heated and dried, and the carbon nanotubes are added to xylene. And triethylenetetramine is added, and after ultrasonic treatment, the solution is heated. The filter is filtered through a filter paper, the carbon nanotubes remaining on the filter paper are dried and the carbon nanotubes are surface-treated, and the diaphragm is formed from a composite material in which the matrix resin is reinforced with the carbon nanotubes thus surface-treated. A method for manufacturing a diaphragm for an electroacoustic transducer.

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