JP2013228097A - Composite vibration damping material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration damping material which exhibits a further effective vibration damping effect than those of conventional technologies.SOLUTION: In a composite vibration damping material 1, an acicular high-permittivity dielectric 3 comprising titanium dioxide and a piezoelectric fiber 4 comprising an organic material are mixed in a polymer material 2 forming a matrix. Preferably, a flat filler 5 comprising an inorganic material and a conductive particles 6 are also mixed. A cellulose fiber is suitably used as the piezoelectric fiber 4.

Description

  The present invention relates to a vibration damping material that attenuates vibration by converting vibration energy into electrical energy, and more particularly, to a composite vibration damping material that is used to dampen equipment, absorb noise, and the like.

  In recent years, with the development of industrial machines, transportation facilities, and the spread of household appliances, vibrations and noises generated from various devices have been regarded as problems from the viewpoint of health management or environmental conservation. For example, vibrations and noises caused by transportation speedup, especially railways, vibrations and noises caused by vehicles such as automobiles on highways and bridges, vibrations caused by the spread of various precision machines such as audio equipment and personal computers, In particular, low-frequency vibration has been taken up as a social problem, and prevention and reduction measures have become indispensable for future social life.

  Conventionally, in order to prevent vibration and noise, three points are important: (1) increasing mass and increasing rigidity, (2) avoiding resonance, and (3) damping vibration. (See New Material Hand Hook p235 (Maruzen)).

  In contrast to the rigid structure design for preventing vibrations (1) and (2) above, (3) should be a flexible structure, causing vibrations to be freely attenuated and then quickly damped. For such vibration damping, a method for stopping the vibration by rapidly reducing the amplitude by converting the vibration energy of the vibrating body into heat is proposed. Has been. In particular, various types of vibration damping materials that utilize the damping ability of the material itself have been developed.

  Among these, for example, an organic polymer vibration damping material in which a low molecular compound having piezoelectricity, dielectricity, and conductivity is dispersed in a non-piezoelectric organic polymer matrix has been proposed. The action of such a vibration damping material is based on a principle different from that of the conventional vibration damping action. The vibration energy is temporarily converted into electric energy, then converted into heat energy and consumed to attenuate the vibration. It is said that more efficient vibration damping is possible because an electrical energy loss based on the piezoelectric / conductive effect is added (see, for example, Patent Document 1 and Patent Document 2).

On the other hand, for example, when performing fine processing in a semiconductor manufacturing apparatus or the like, more effective vibration damping action is required, and research and development of vibration damping materials are progressing in various technical fields (for example, patents) Reference 3).
Furthermore, in recent years, as a means for damping vibrations in the event of an earthquake, there has been a demand for a simple structure that can obtain a more effective damping action with less material.

JP-A-6-85346 Japanese Patent Laid-Open No. 11-68190 JP 2011-99497 A

  The present invention has been made in consideration of such problems of the conventional technology, and the object of the present invention is to provide a composite damping material capable of exhibiting more effective damping action in a low frequency region. It is to provide.

  In order to solve the above-mentioned object, the present inventor has conducted extensive research and as a result, the polymer material used as a matrix is mixed with a piezoelectric fiber made of an acicular high dielectric constant dielectric material and an organic material. It has been found that a very effective damping material against frequency vibration can be obtained, and the present invention has been completed.

The present invention based on such knowledge is a composite vibration damping material in which a needle-like high dielectric constant dielectric material and piezoelectric fiber made of an organic material are mixed in a polymer material as a matrix.
In the present invention, the polymer material used as a matrix is a mixture of a needle-like high dielectric constant dielectric, a piezoelectric fiber made of an organic material, a flat filler made of an inorganic material, and conductive fine particles. It is a composite vibration damping material.
The present invention is also effective when the needle-like high dielectric constant dielectric is made of titanium dioxide.
In the present invention, the needle-like high dielectric constant dielectric is also effective when a conductor layer is provided on the surface of a core made of needle-like titanium dioxide.
The present invention is also effective when the piezoelectric fiber made of the organic material is made of cellulose fiber.

  ADVANTAGE OF THE INVENTION According to this invention, the damping material which can exhibit more effective damping action in a low frequency area | region can be provided.

Schematic cross-sectional view showing the schematic configuration of the composite vibration damping material of the present invention (A): Schematic diagram showing the dimensional relationship of the acicular dielectric used in the present invention, (b): sectional view showing the configuration of the acicular dielectric having a conductor layer on the surface of titanium dioxide, (c): Schematic showing the dimensional relationship of the piezoelectric fibers used in the present invention Schematic cross-sectional view showing the state of charge generation when vibration is applied to the composite damping material of the present invention (A)-(c): Schematic diagram illustrating the principle of the present invention The graph which shows the relationship between the frequency and loss factor in the Example of this invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of the composite vibration damping material of the present invention. 2A is a schematic diagram showing the dimensional relationship of the acicular dielectric used in the present invention, and FIG. 2B shows the configuration of the acicular dielectric provided with a conductive layer on the surface of titanium dioxide. FIG. 2C is a schematic view showing the dimensional relationship of the piezoelectric fiber used in the present invention.

As shown in FIG. 1, a composite damping material 1 according to the present invention includes a polymer material 2 serving as a matrix, and a needle-like high dielectric constant dielectric 3 and a piezoelectric fiber 4 composed of an organic material. Preferably, a flat filler 5 made of an inorganic material and conductive fine particles 6 are further mixed.
In the present invention, the polymer material 2 serving as a matrix is not particularly limited, and various elastomers and polymer resins can be used.

Examples of the elastomer that can be used in the present invention include acrylic rubber (ACR), butyl rubber (IIR), acrylonitrile-butadiene rubber (NBR), acrylonitrile-butadiene rubber (NBR / PVC) blended with vinyl chloride resin, and styrene- Examples include butadiene rubber (SBR), butadiene rubber (BR), natural rubber (NR), isoprene rubber (IR), butyl rubber (IIR), ethylene propylene rubber (EPM), and chloroprene rubber (CR).
Among these, from the viewpoint of improving weather resistance and wear resistance, it is preferable to use acrylonitrile-butadiene rubber (NBR / PVC) blended with a vinyl chloride resin.

  On the other hand, examples of the polymer resin that can be used in the present invention include polylactic acid resin, polyurethane resin, acrylate resin, epoxy resin, polypropylene resin, polycarbonate resin, polyester resin, polyether resin, vinyl acetate resin, and polymethacrylic acid. Methyl resin, polyvinylidene fluoride resin, polystyrene resin, ethylene-vinyl acetate copolymer, ethylene-vinyl chloride copolymer, ethylene-methacrylate copolymer, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer Chlorinated polyethylene, chlorinated polypropylene, chlorinated polybutylene and the like.

The acicular high dielectric constant dielectric (hereinafter referred to as “acicular dielectric”) 3 used in the present invention is made of acicular titanium dioxide (TiO ₂ ), for example. In addition, as a crystal form of titanium dioxide, a rutile type can be suitably used.
In this specification, “needle shape” means a shape in which the length L ₁ of the major axis is larger than the diameter L _{2 of the} minor axis, as shown in FIG. Means the same.

Here, as the acicular dielectric 3, it is preferable that the aspect ratio, that is, the ratio (L ₁ / L ₂ ) between the major axis length L ₁ and the minor axis diameter L ₂ is 10 to 30.
The aspect ratio of the acicular dielectric 3 is preferably as large (elongated) as possible from the viewpoint of increasing the generated electric energy and exhibiting a more effective vibration damping action in the low frequency region.

However, it is practically difficult to manufacture a product having an aspect ratio exceeding 30.
On the other hand, when the aspect ratio of the acicular dielectric 3 is less than 10, sufficient electric energy cannot be generated.

The details of the acicular dielectric 3 are not clear, but the molecular arrangement is unidirectional due to, for example, the stress caused by the pressure during particle production or the pressure during mixing (kneading) in the polymer material 2. It is thought that the so-called monodomain structure is suitable.
Such a needle-like dielectric 3 is considered to have a molecular arrangement structure that exhibits a piezoelectric effect and in which the generated electric energy easily flows along the longitudinal direction of the particles.

In the present invention, as shown in FIG. 2 (b), the conductive layer 30 can be provided on the surface of the above-described titanium dioxide of the acicular dielectric 3 as a nucleus.
By providing the conductor layer 30 on the surface of the titanium dioxide of the needle-shaped dielectric 3, the magnitude of the current flowing on the surface of the needle-shaped dielectric 3 can be increased, so that a smaller amount of the needle-shaped dielectric 3 is provided. Can effectively control vibration.

In the case of the present invention, the material of the conductor layer 30 is not particularly limited, but from the viewpoint of improving the conductivity with ease of production and a smaller amount, tin dioxide doped with antimony (Sb) (SnO ₂ ) can be suitably used.

In this case, the thickness of the conductor layer 30 is preferably set to 1 to 20 μm when printed.
On the other hand, the thickness of the conductor layer 30 can be set to 0.1 to 100 μm in the case of vapor deposition.

  On the other hand, the resistivity of the acicular dielectric 3 according to the present invention (including that formed with the conductor layer 30) is preferably 2 to 80 Ω · cm, and more preferably 10 to 60 Ω · cm.

The piezoelectric fiber 4 made of an organic material used in the present invention is not particularly limited, but for example, those made of cellulose can be suitably used.
As the piezoelectric fiber 4, powdery cellulose (cellulose powder) having a small aspect ratio can be used in addition to those having a large aspect ratio (cellulose fiber).
Cellulose, which is wood, is known to have piezoelectricity, and the cellulose fiber (powder) used in the present invention also has piezoelectricity.

The aspect ratio of the piezoelectric fiber 4, that is, the ratio of the major axis length l ₁ to the minor axis diameter l ₂ (l ₁ / l ₂ ) (see FIG. 2 (c)) is generated based on the electric dipole. From the viewpoint of increasing the electrical energy to be applied and from the viewpoint of exhibiting more effective vibration damping action in the low frequency region, it is preferable to use a fiber shape that is as large as possible (elongated).
However, in view of the fact that it is actually difficult to manufacture a product having an aspect ratio exceeding 10, it is more preferable to use a piezoelectric fiber 4 having an aspect ratio of 2 to 10.

In the present invention, the compounding amount of the acicular dielectric 3 in the composite damping material 1 is not particularly limited, but is preferably set to 3 wt% to 7 wt%.
If the blending amount of the acicular dielectric 3 is less than 3% by weight, a sufficient vibration damping effect cannot be obtained, while if it exceeds 7% by weight, it becomes brittle after molding, which is not preferable.
On the other hand, the blending amount of the piezoelectric fiber 4 made of an organic material in the composite damping material 1 is not particularly limited, but is preferably set to 4 to 10% by weight, more preferably 8% by weight. -10% by weight.
When the blending amount of the piezoelectric fiber 4 made of an organic material is less than 4% by weight, a sufficient vibration damping effect cannot be achieved, and when it exceeds 10% by weight, it is difficult to uniformly disperse. Therefore, it is not preferable.

In this invention, the flat filler 5 which consists of inorganic materials, and the electroconductive fine particles 6 can be mix | blended as needed.
The flat filler 5 made of an inorganic material used in the present invention is intended to further improve the vibration damping capability and obtain desired mechanical properties (such as elastic modulus) as the entire composite material.
As such a flat filler 5, what consists of layered mica (mica), for example can be used suitably.

  In the case of the present invention, the blending amount of the filler 5 made of an inorganic material is not particularly limited, but is preferably set to 10% by weight to 30% by weight in view of the above-described object.

The conductive fine particles 6 used in the present invention are for improving and adjusting the conductivity of the composite material as a whole.
As such conductive fine particles 6, for example, those made of carbon black can be suitably used.
In addition, as the conductive fine particles 6, those previously added to the polymer material 2 can be used.

  In the present invention, the blending amount of the conductive fine particles 6 in the composite vibration damping material 1 is not particularly limited, but is preferably set to 5% by weight to 20% by weight in view of the above-described object.

An ordinary method may be used to obtain the composite vibration damping material 1 and the molded body thereof according to the present invention.
That is, a predetermined amount of the above-described acicular dielectric 3, piezoelectric fiber 4 made of an organic material, flat filler 5 made of an inorganic material, and conductive fine particles 6 are added to the polymer material 2 for the matrix. Kneading at a predetermined temperature, for example, after hot roll press molding, it may be cut into a predetermined size.

The composite vibration damping material 1 of the present invention can be used as molded articles having various shapes.
For example, in addition to a film-shaped molded body, various shapes such as a disk shape, a cylindrical shape, a rectangular parallelepiped shape, a polyhedron shape, and a spherical shape can be used.
Moreover, it can be formed into a fiber and used as a cloth or used as a non-woven fabric.

FIG. 3 is a schematic cross-sectional view showing a charge generation state when vibration is applied to the composite vibration damping material of the present invention, and FIGS. 4A to 4C are schematic views showing the principle of the present invention. is there.
When periodic vibration is applied to the composite vibration damping material 1 of the present invention, the vibration energy causes displacement between layers in the flat filler 5 made of an inorganic material in the polymer material 2, and heat is generated by this mechanical action. Occurs and absorbs vibration.

Further, in the present invention, as shown in FIG. 3, a potential difference is periodically generated between the both ends of the piezoelectric fiber 4 in the polymer material 2 due to the piezoelectric effect (electric dipoles 4 a and 4 b).
In this case, as the aspect ratio of the piezoelectric fiber 4 increases, the electric dipoles 4a and 4b generated in the piezoelectric fiber 4 increase.
Then, an alternating current caused by the electric dipoles 4a and 4b generated in a large number of piezoelectric fibers 4 flows through a conductive path in the composite material (compound), and electric energy by the alternating current is consumed as Joule heat, The vibration energy in the composite damping material 1 is attenuated.
On the other hand, due to the piezoelectric effect of the acicular dielectric 3, a potential difference is periodically generated between both ends (electric dipoles 3a and 3b).

In addition, in the present invention, as shown in FIG. 4A, electric dipoles 4a and 4b generated in the piezoelectric fiber 4 are present in the vicinity of the acicular dielectric 3, so that As shown in FIG. 4 (b), the acicular dielectric 3 is disposed in the electric field F generated by the electric dipoles 4a and 4b.
As a result, as shown in FIG. 4C, electric dipoles 3 c and 3 d caused by interface polarization are generated at the interface between the acicular dielectric 3 and the polymer material 2.

An electric circuit is formed on the surface of the needle-shaped dielectric 3 by the electric dipoles 3a and 3d and the electric dipoles 3b and 3c generated in the needle-shaped dielectric 3, and an alternating current is generated on the surface of the needle-shaped dielectric 3. Flows.
As a result, the electric energy due to the alternating current on the surface of the needle-shaped dielectric 3 is consumed as Joule heat, and the vibration energy in the composite damping material 1 is attenuated.

In general, when the resistance of a piezoelectric composite material in which particles having a piezoelectric effect are mixed is R, the capacitance of the piezoelectric particles is C, and the frequency of vibration to be damped is ω, the impedance matching condition is R = 1 / ωC. It is known that vibration is damped most rapidly when is established.
Therefore, in the present invention, a desired vibration damping effect can be obtained by setting an appropriate conductivity corresponding to the natural frequency of the composite vibration damping material 1.

  As described above, in the case of the present invention, the electric dipoles 3a and 3b due to the piezoelectric effect are generated in the acicular dielectric 3 during vibration, and further, the electric dipoles 4a and 4b generated in the piezoelectric fiber 4 are generated. Since the resulting electric dipoles 3c and 3d are generated, a large current flows due to the electric dipoles 3a to 3d on the surface of the conductive acicular dielectric 3, and this electric energy is converted into Joule heat. A large amount is consumed and vibration is absorbed.

  As described above, according to the present invention, the vibration energy is attenuated by the synergistic effect of the piezoelectric fibers 4 and the electric dipoles 3a to 3d of the needle-like dielectric 3, so that a more effective vibration damping action can be achieved compared to the prior art. It can be demonstrated.

Moreover, since electric dipoles due to interfacial polarization occur at a low frequency (less than 500 Hz) due to the needle shape (see, for example, Japanese Patent Laid-Open No. 10-312191), according to the present invention, a device that vibrates at a low frequency. Therefore, it is possible to provide a composite vibration damping material that performs vibration damping under optimum conditions.
Further, by mixing the flat filler 5 made of an inorganic material, vibration energy is attenuated by the mechanical action of the flat filler 5 made of the inorganic material, and the piezoelectric fiber 4 and the needle-like dielectric 3 The damping of vibration energy due to the synergistic effect of the electric dipoles 3a to 3d makes it possible to exhibit a more effective vibration damping action. By mixing the conductive fine particles 6, the conduction of the composite material as a whole is improved. The rate can be improved and adjusted.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples.
<Example 1>
A sample of the composite damping material of Example 1 was prepared using the following materials.
As the polymer material for the matrix, acrylonitrile-butadiene rubber (NBR / PVC: trade name NBRPVC601A manufactured by INB Planning) blended with a vinyl chloride resin was used.
Conductive fine particles made of carbon black are added to the polymer material.
As acicular high dielectric constant dielectric, acicular titanium dioxide fine particles having a conductor layer (trade name: FT-4000, manufactured by Ishihara Sangyo Co., Ltd., major axis length: 10 μm, minor axis diameter: 0.5 μm, aspect ratio : 20) was used.
As a piezoelectric fiber made of an organic material, a cellulose fiber having an aspect ratio of 2.11 (trade name: Solka Flock # 100, manufactured by Imazu Pharmaceutical Co., Ltd., major axis length: 40 μm, minor axis diameter: 19 μm) was used.
As the flat filler, layered mica (trade name, Clarite Mica Kuraray Co., Ltd.) was used.
The above-mentioned NBR / PVC of 48% by weight (of which conductive fine particles are 15% by weight), the above-mentioned acicular titanium dioxide fine particles of 3.1% by weight, cellulose fiber 4.3% by weight, mica 20% by weight, vibration suppression 20% by weight of organic composite material, 3.1% by weight of processing aid and 1.5% by weight of cross-linking agent are added and kneaded at a temperature of 140 ° C. After hot roll press molding, the size is 10 mm × 200 mm. Cut to obtain a test film having a thickness of 1 mm.
<Example 2>
Other than using piezoelectric fiber made of organic material, cellulose fiber with aspect ratio of 3.44 (trade name: Solka Flock # 40, Imazu Pharmaceutical Co., Ltd., major axis length: 55 μm, minor axis diameter: 16 μm) A sample of a damping material was prepared under the same conditions as in Example 1.
<Example 3>
Other than using piezoelectric fiber made of organic material, cellulose fiber with an aspect ratio of 6.22 (trade name Solkaflock # 10, Imazu Pharmaceutical Co., Ltd., major axis length: 100 μm, minor axis diameter: 16 μm) A sample of a damping material was prepared under the same conditions as in Example 1.
<Comparative example>
A sample of the damping material was prepared under the same conditions as in Example 1 except that the piezoelectric fibers made of the fine particles of acicular titanium dioxide and the organic material were not added to the NBR / PVC described above.
This vibration damping material contains 40% by weight of conductive fine particles.
For the samples of Examples 1 to 3 and the comparative example, the frequency dependence of the loss factor (Tan δ) was measured by the central vibration method (10 × 200 × 0.8 mm 12.35 g steel plate).
As a measurement system, an oscillator is Type 2825, an amplifier is Type 2718, an exciter is Type 4809, an acceleration sensor is Type 8001 (both manufactured by B & K), and a personal computer is used to control each device. Using.
In this case, the resonance frequency was measured from the first order to the seventh order. The measurement result of this loss factor is shown in FIG.
As is clear from FIG. 5, the damping materials of Examples 1 to 3 have a loss factor more than twice that of the damping material of the comparative example in the low frequency range of about 60 Hz to about 500 Hz. Thus, the effect of the present invention could be verified.
Moreover, the damping materials of Examples 1 to 3 are in the order of increasing aspect ratios of cellulose fibers, which are piezoelectric fibers, in a low frequency range of about 60 Hz to about 500 Hz, that is, Example 3, Example 2, The loss factor increased in the order of Example 1.
Furthermore, this tendency was not changed even in a frequency region exceeding 500 Hz.
From this result, it is understood that greater electrical energy is generated in the piezoelectric fiber by increasing the aspect ratio of the piezoelectric fiber.

DESCRIPTION OF SYMBOLS 1 ... Composite damping material, 2 ... Polymer material, 3 ... Acicular high dielectric constant dielectric material, 4 ... Piezoelectric fiber, 5 ... Flat filler, 6 ... Conductive fine particle

Claims (5)

  A composite damping material in which a high polymer dielectric material is mixed with a needle-like high dielectric constant dielectric material and piezoelectric fiber made of an organic material.   A composite damping material in which a high polymer dielectric material is mixed with acicular high dielectric constant dielectric, piezoelectric fiber made of organic material, flat filler made of inorganic material, and conductive fine particles. material.   The composite vibration damping material according to claim 1, wherein the acicular high dielectric constant dielectric is made of titanium dioxide.   The composite vibration damping material according to any one of claims 1 to 3, wherein the acicular high dielectric constant dielectric is provided with a conductor layer on a surface of a core made of acicular titanium dioxide.   The composite vibration damping material according to any one of claims 1 to 4, wherein the piezoelectric fiber made of the organic material is made of cellulose fiber.

Images