JP2005203590A - Piezoelectric transduction composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric transduction composite material where a load on environment at the time of wasting is small, costs are reduced and mass productivity is excellent, piezoelectric transduction material showing sufficient piezoelectricity is used, and vibration etc. from outside is absorbed as strain energy and can be transduced to electricity. <P>SOLUTION: The piezoelectric transduction composite material has a domain showing piezoelectricity, which is formed of piezoelectric transduction material containing biodegradable resin in a matrix material. In particular, a mode where the biodegradable resin is polylactic acid, a mode where the domain showing piezoelectricity is a thready piece obtained by cutting a compact consisting of piezo-electric transduction material, and a mode where a damping factor ((piezoelectricity α - piezoelectricity β)/ piezoelectricity α) calculated from the piezoelectricity α of the domain at a room temperature before heating and the piezoelectricity β at the room temperature after keeping the heated state of the domain at 85°C for 7 days is ≤0.1 are desirable. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a piezoelectric conversion composite material that can be suitably used in various fields as a vibration damping material or the like.

  Damping materials are materials that absorb vibrations, and many have been developed in the past. Recently, materials using piezoelectric conversion have attracted attention. The damping material using the piezoelectric conversion generally has a piezoelectric element portion and a matrix portion. The vibration absorption process in the damping material is as follows. That is, firstly, the matrix portion receives vibration energy from the outside as strain, the piezoelectric element portion receives strain as the strain, and converts this into electricity, and as Joule heat, the outside of the damping material. discharge. As a result, the vibration energy from the outside is absorbed by the damping material, converted into heat, and released from the damping material.

The following three materials have been proposed as vibration damping materials using the piezoelectric conversion.
The first is an organic-inorganic composite damping material. The organic-inorganic composite vibration damping material is obtained by dispersing a piezoelectric conversion material made of an inorganic material such as barium titanate in a matrix made of an organic material such as rubber (see Patent Documents 1 to 3).
The second is an organic piezoelectric film damping material. The organic piezoelectric film damping material is, for example, a film showing piezoelectricity such as polyvinylidene fluoride (PVDF) (see Non-Patent Document 1).
The third is an organic-organic composite damping material. The organic-organic composite vibration damping material is, for example, a material in which a piezoelectric conversion material made of organic low molecules such as phenolic substances is dispersed in a matrix made of an organic material such as rubber (see Patent Documents 4 to 5). .

However, these vibration damping materials have the following problems. That is, in the case of the organic-inorganic composite vibration damping material, it is difficult to obtain a single crystal of the inorganic material such as barium titanate, and the difference in elastic modulus between the inorganic material and the matrix is too large. There is a problem that vibration transmission from the matrix is not sufficient and the matrix is easily damaged by strain. In addition, the organic piezoelectric film damping material has a problem that the piezoelectric conversion characteristics (hereinafter sometimes abbreviated as “piezoelectricity”) deteriorate with time and have an adverse effect on the environment at the time of disposal. In addition, with a general door size of 200 cm × 100 cm, there is a problem that the optimum resistance value in an electric circuit necessary for obtaining effective vibration damping characteristics is 0.25Ω, and the resistance value is practically small and cannot be realized. (See Patent Document 6). In addition, in the case of the organic-organic composite vibration damping material, since the orientation of organic low molecules such as the phenolic material is not sufficient, the piezoelectricity is not sufficient, and the function of the vibration damping material is not necessarily sufficient. is there. Furthermore, among the organic materials, ferroelectric polymers such as PVDF having excellent piezoelectricity are widely used, but the glass transition temperature (Tg) is low and the piezoelectricity is easily attenuated by heat. This is unsuitable for applications requiring heat resistance, and there is a problem that the initial performance cannot be maintained for a long time. On the other hand, in the case of ferroelectric liquid crystal, there is a problem that it is difficult to increase the film thickness, and in the case of cellulose, since piezoelectricity is not derived from polarity, there is a problem that it is essentially small.
For this reason, there is no such problem in the prior art, it can absorb external vibrations etc. as strain energy, convert it efficiently into electricity, and release it as heat, even when kept for a long time under high temperature conditions Piezoelectric composite material that maintains sufficient piezoelectricity and can be suitably used for applications that require heat resistance, but also has a low environmental impact when disposed of and can be easily disposed of. Is not provided yet.

Japanese Patent Laid-Open No. 5-31845 JP-A-5-240298 JP-A-6-126909 JP 2000-86900 A JP 2000-273435 A Japanese Patent Laid-Open No. 11-68190 Masao Sumita, “Sound-absorbing and insulating structure using piezoelectric film”, functional materials, CMC Publishing Co., Ltd., November 1995, Vol.15, No.11

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, it exhibits sufficient piezoelectricity without performing a polling treatment by an electric field, can be suitably used in various fields as a vibration damping material, etc., and is also suitably used for applications requiring heat resistance, By using a piezoelectric conversion material that can be mass-produced at low cost, has excellent handling characteristics, and has a low environmental impact during disposal, it absorbs external vibrations as strain energy and efficiently converts it into electricity. And it aims at providing the piezoelectric conversion composite material which can be discharge | released as a heat | fever.

Means for solving the above problems are as follows. That is,
<1> A piezoelectric conversion composite material comprising a domain exhibiting piezoelectricity in a matrix material, wherein the domain exhibiting piezoelectricity is formed of a piezoelectric conversion material containing a biodegradable resin. . In the piezoelectric conversion composite material, vibration energy from the outside is received as strain by the matrix material, and distortion of the matrix material is received as strain by the piezoelectric conversion material that forms a domain exhibiting piezoelectricity. It is converted to electricity and released to the outside as Joule heat. When the piezoelectric conversion composite material is disposed in soil, at least the domain is decomposed by microorganisms or the like.
<2> The piezoelectric conversion composite material according to <1>, wherein the matrix material includes a biodegradable resin. When the piezoelectric conversion composite material is discarded in soil, the domains and the matrix are decomposed by microorganisms or the like.
<3> The piezoelectric conversion composite material according to any one of <1> to <2>, wherein the biodegradable resin is at least one selected from aliphatic polyester resins. In the piezoelectric conversion composite material, since the biodegradable resin is at least one selected from aliphatic polyester resins, piezoelectric conversion is efficiently performed by the domains.
<4> The piezoelectric conversion composite material according to <3>, wherein the aliphatic polyester resin is at least one selected from polylactic acid-based aliphatic polyester resins. In the piezoelectric conversion composite material, since the aliphatic polyester resin is at least one selected from polylactic acid-based aliphatic polyester resins, piezoelectric conversion is efficiently performed by the domains.
<5> The piezoelectric conversion composite material according to <4>, wherein the polylactic acid-based aliphatic polyester resin is polylactic acid. In the piezoelectric conversion composite material, since the polylactic acid-based aliphatic polyester resin is polylactic acid, the piezoelectric conversion is efficiently performed by the domains.
<6> The piezoelectric conversion composite material according to any one of <1> to <5>, wherein the piezoelectric conversion material contains an adhesive polymer.
<7> The piezoelectric conversion composite material according to any one of <1> to <6>, wherein the domain exhibiting piezoelectricity is a fine piece formed by cutting a formed body of a piezoelectric conversion material. In the piezoelectric conversion composite material, the strain received by the matrix material is received as a strain by a strip formed by cutting a molded body of the piezoelectric conversion material, and this is converted into electricity and released to the outside as Joule heat. .
<8> The piezoelectric conversion composite material according to <7>, wherein the fine piece is selected from at least one of a thread-like piece, a film-like piece, and a granular piece. In the piezoelectric conversion composite material, the strain received by the matrix is received as strain by a strip selected from at least one of a thread-like piece, a film-like piece, and a granular piece, and this is converted into electricity, and Joule heat To the outside.
<9> The piezoelectric conversion composite material according to any one of <7> to <8>, wherein the direction and direction of polarization in the strips are irregular between the strips. In the piezoelectric conversion composite material, vibration energy from an arbitrary direction is efficiently piezoelectrically converted in the strip.
<10> The piezoelectric conversion composite material according to any one of <7> to <8>, wherein the direction and direction of polarization in the strips are substantially the same between the strips. In the piezoelectric conversion composite material, vibration energy from a specific direction is efficiently piezoelectrically converted in the strip.
<11> The piezoelectric conversion composite material according to any one of <7> to <10>, wherein the thin piece is a thread-like piece, and the diameter, length, and material of the thread-like piece are substantially the same. In the piezoelectric conversion composite material, there is little difference in piezoelectric frequency characteristics between the strips. For this reason, the piezoelectric conversion composite material is suitably used when it efficiently receives vibration energy in a specific frequency region from the outside.
<12> The piezoelectric conversion composite material according to any one of <7> to <10>, wherein the thin piece is a thread-like piece and at least one of a diameter, a length, and a material of the thread-like piece is different. In the piezoelectric conversion composite material, there is a difference in piezoelectric frequency characteristics between the strips. For this reason, the piezoelectric conversion composite material is suitably used when receiving vibration energy in all frequency ranges from the outside on average.
<13> The thin piece is a film-like piece, and the area, thickness, and material of the film-like piece are substantially the same <
The piezoelectric conversion composite material according to any one of <7> to <10>. In the piezoelectric conversion composite material, there is little difference in piezoelectric frequency characteristics between the strips. For this reason, the piezoelectric conversion composite material is suitably used when it efficiently receives vibration energy in a specific frequency region from the outside.
<14> The piezoelectric conversion composite material according to any one of <7> to <10>, wherein the thin piece is a film-like piece, and at least one of the area, thickness, and material of the film-like piece is different. In the piezoelectric conversion composite material, there is a difference in piezoelectric frequency characteristics between the strips. For this reason, the piezoelectric conversion composite material is suitably used when receiving vibration energy in all frequency ranges from the outside on average.
<15> The piezoelectric conversion composite material according to any one of <1> to <14>, wherein the elastic modulus of the strip and the matrix material is substantially the same. The piezoelectric conversion composite material is excellent in piezoelectricity because the distortion of the matrix is efficiently transmitted to the strip.
<16> The piezoelectric conversion composite material according to any one of <1> to <15>, wherein the matrix material contains a conductive material. In the piezoelectric conversion composite material, the electric energy converted from the strain energy by the strip is efficiently propagated through the matrix material through the conductive material and is efficiently released to the outside as Joule heat. .
<17> The piezoelectric conversion composite material according to <16>, wherein the conductive material is selected from conductive fine particles and a conductive filler. In the piezoelectric conversion composite material, electric energy converted from strain energy by the strips efficiently propagates in the matrix material through the conductive material selected from the conductive fine particles and conductive filler. As a Joule heat, it is efficiently released to the outside. In the piezoelectric conversion composite material, since the conductive fine particles are dispersed in the matrix material, electric energy converted from strain energy by the strips is efficiently propagated by the conductive fine particles, and Joule heat Is efficiently released to the outside.
<18> The piezoelectric conversion composite material according to <17>, wherein the conductive fine particles are at least one selected from metal fine particles, semiconductor fine particles, carbon black, fullerene, and carbon nanotubes.
<19> Decay factor ((piezoelectric α− The piezoelectric conversion composite material according to any one of <1> to <18>, wherein the piezoelectricity β) / piezoelectricity α) is 0.1 or less. Since the piezoelectric conversion composite material has an attenuation factor of 0.1 or less, piezoelectricity is sufficiently maintained even when the piezoelectric conversion composite material is held for a long time under a high temperature condition.
<20> The piezoelectric conversion composite material according to any one of <1> to <19>, which is used as a vibration damping material. The piezoelectric conversion composite material is suitably used in various fields as a damping material capable of effectively absorbing vibration energy.
<21> In the above <20>, where ω is the frequency of vibration to be damped, C is the capacitance of the domain exhibiting piezoelectricity, and R is the conductive resistance of the matrix material, R≈1 / ωC. This is a piezoelectric conversion composite material. Since the piezoelectric conversion composite material satisfies the above conditions, it exhibits excellent vibration damping properties.

  According to the present invention, conventional problems can be solved, and it can be suitably used in various fields as a vibration damping material, etc., and does not require a poling treatment by an electric field, and is sufficient even when held for a long time under high temperature conditions Piezoelectric conversion material that is suitable for applications requiring high heat resistance and heat resistance, can be mass-produced at low cost, has excellent handleability, and has a low environmental impact during disposal. By using it, it is possible to provide a piezoelectric conversion composite material that absorbs external vibration or the like as strain energy, efficiently converts it into electricity, and can release it as heat.

(Piezoelectric conversion composite material)
The piezoelectric conversion composite material of the present invention has a domain exhibiting piezoelectricity in the matrix material, and further includes other materials as necessary.

-Domain showing piezoelectricity-
The domain exhibiting piezoelectricity needs to be formed of a piezoelectric conversion material.

  The piezoelectric conversion material includes at least a biodegradable resin, and may further include other components appropriately selected as necessary.

  There is no restriction | limiting in particular as said biodegradable resin, According to the objective, it can select suitably, Natural product origin biodegradable resin, chemically synthesized biodegradable resin, others, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the natural product-derived biodegradable resin include chitin / chitosan, alginic acid, gluten, collagen, polyamino acid, bacterial cellulose, pullulan, curdlan, polysaccharide by-products, starch, modified starch, and microorganism-produced polyester (biopolyester). ), Etc.

Examples of the chemically synthesized biodegradable resin include aliphatic polyester, aliphatic / aromatic polyester, polyvinyl alcohol (PVA), polyurethane (PU), and the like.
Examples of the aliphatic polyester include polyhydroxyalkanoates such as poly-3-hydroxybutyrate (PHB) and poly-3-hydroxyvalerate, polycaprolactone (PCL), polybutylene succinate (PBS), poly Examples include butylene succinate adipate (PBSA), polyethylene succinate (PES), polyglycolic acid (PGA), and polylactic acid (PLA).

  As said other thing, the carbonate copolymer of aliphatic polyester, the copolymer of aliphatic polyester and polyamide, etc. are mentioned, for example.

  Among the biodegradable resins, natural product-derived biodegradable resins and chemically synthesized biodegradable resins are preferable. Among them, aliphatic polyester resins are more preferable in terms of excellent moldability, heat resistance, impact resistance, and the like. Among them, polylactic acid (PLA) aliphatic polyester resin is particularly preferable, and polylactic acid is most preferable in terms of excellent piezoelectricity.

  Examples of the polylactic acid (PLA) aliphatic polyester resin include polymers of oxyacids such as lactic acid, malic acid, and glucose acid, and copolymers thereof. Of these, hydroxycarboxylic acid aliphatic polyester resins represented by polylactic acid are particularly preferred.

  The method for producing the hydroxycarboxylic acid-based aliphatic polyester resin is not particularly limited and may be appropriately selected depending on the intended purpose. For example, lactide obtained by ring-opening polymerization of lactide which is a cyclic diester and a corresponding lactone is used. And lactic acid direct dehydration condensation method, dehydration condensation polymerization method of aliphatic diol and dicarboxylic acid. Moreover, as a catalyst used at the time of manufacture, tin, antimony, zinc, titanium, iron, an aluminum compound, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Among these, tin, an aluminum compound, and the like are preferable, and tin octylate and aluminum acetylacetonate are more preferable.

-Other ingredients-
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, the polymer for adhesion | attachment etc. which make film-forming easy are mentioned suitably. The adhesive polymer may be a known binder resin.
There is no restriction | limiting in particular as said well-known binder resin, According to the objective, it can select suitably, For example, a thermoplastic resin, rubber | gum (elastomer type), an adhesive, a monomer thru | or oligomer, a polymer alloy, a polyimide, a natural product , Inorganic substances, and the like.

Examples of the thermoplastic resin include polyvinyl acetate (PVAc), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), acrylic copolymer (acrylic), polyethylene (PE), and ethylene-acetic acid copolymer (EVA). , Vinyl chloride plus sol, polyvinyl chloride-vinyl acetate copolymer, polyvinyl pyrrolidone, nylon 11,12, copolymer nylon, polyethylene terephthalate cocondensate, polybutylene terephthalate, urea resin, melamine resin, phenol resin, resorcinol resin , Epoxy resin, polyurethane, vinyl urethane, and the like.
Examples of the rubber include polyisoprene natural rubber, synthetic polyisoprene rubber, polychloroprene, acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, styrene-butadiene-vinylpyridine terpolymer, polyisobutylene, and butyl rubber. , Polysulfide, room temperature vulcanizing silicone rubber, chlorinated rubber, brominated rubber, graft polychloroprene, styrene-isoprene-styrene, styrene-butadiene-styrene, and the like.

Examples of the pressure-sensitive adhesive include pressure-sensitive adhesives, acrylics, and silicones.
Examples of the monomer or oligomer include cyanoacrylate, ultraviolet curable adhesive, visible light curable adhesive, and electron beam curable adhesive.
Examples of the polymer alloy include polyvinyl formal or butyral / phenolic, nitrile rubber / phenolic, nitrile rubber / epoxy, liquid nitrile rubber / epoxy, epoxy / phenolic, and the like.
Examples of the natural product include starch and dextrin.
Examples of the inorganic material include sodium silicate and ceramics.

  There is no restriction | limiting in particular as content in the said piezoelectric conversion material of the said other component, It can select suitably in the range which does not impair the effect of this invention.

The domain exhibiting piezoelectricity is preferably formed of a strip formed by cutting a molded body made of the piezoelectric conversion material.
The shape of the strip is not particularly limited as long as it exhibits piezoelectricity, and can be appropriately selected according to the purpose. However, it can be suitably selected from at least one of a thread-like piece, a film-like piece and a granular piece. it can.

There is no restriction | limiting in particular about the magnitude | size, area, diameter, length, thickness, number, etc. of the said strip, According to the objective, it can select suitably.
When the strip is the filamentous piece, the diameter, length and material of the filamentous piece may be substantially the same, or at least one of the diameter, length and material of the filamentous piece may be different. . In the former case, since there is little difference in the frequency characteristics of the piezoelectric conversion capacity for each strip, the piezoelectric conversion composite material is suitable for receiving vibration energy from the outside substantially uniformly. In the latter case, the piezoelectric conversion composite material is suitable for each strip. Since there is a difference in conversion ability, the piezoelectric conversion composite material is suitable for efficiently receiving vibration energy in a specific frequency region from the outside.
When the strip is the membrane piece, the area, thickness and material of the membrane piece may be substantially the same, or at least one of the area, thickness and material of the membrane piece may be different. Good. In the former case, since there is little difference in the frequency characteristics of the piezoelectric conversion capacity for each membrane strip, the piezoelectric conversion composite material is suitable for receiving vibration energy from the outside substantially uniformly. In the latter case, the membrane strip is suitable for each membrane strip. Therefore, the piezoelectric conversion composite material is suitable for receiving vibration energy in all frequency ranges from the outside on average.

When the strip is formed of an optically active polymer such as the polylactic acid or the bacterial cellulose, since the strip is a non-polarizable material, the strip does not have a polarization component. The strips are present in the matrix, for example, in the following manner.
That is, as shown in FIG. 1A, the strips are present in the matrix 20 so that the uniaxial orientation of the optically active polymer in the strips 5 is irregular between the strips. Alternatively, as shown in FIG. 1B or 1C, the optically active polymer in the strip 5 exists in the matrix 20 so that the uniaxial orientation directions of the strips are substantially the same between the strips. May be. In the former case, vibration energy from an arbitrary direction is preferable in that piezoelectric conversion can be performed efficiently (without directivity) in the strip, and in the latter case, vibration energy from a specific direction is efficient in the strip. It is preferable in that the piezoelectric conversion is possible (with directivity).

On the other hand, when the strip is formed of the polarizable piezoelectric conversion material, the strip has a polarization component and is present in the matrix in the following manner, for example.
That is, as shown in FIG. 2 (A), the direction of the polarization in the strip 10 is irregular between the strips (the direction of the polarization vector is random between the strips). May exist in the matrix 20, and as shown in FIG. 2B or 2 C, the direction and direction of polarization in the strip 10 are substantially the same between the strips (the polarization It may be present in the matrix 20 such that the direction and orientation are substantially the same between the strips and the polarization does not cancel between the strips). In the former case, vibration energy from an arbitrary direction is preferable in that piezoelectric conversion can be performed efficiently (without directivity) in the strip, and in the latter case, vibration energy from a specific direction is efficient in the strip. It is preferable in that the piezoelectric conversion is possible (with directivity).

  There is no restriction | limiting in particular as an elastic modulus in the said strip, Although it can select suitably according to the objective, It is preferable that it is substantially the same as the elastic modulus of the said matrix material. In this case, since the distortion of the matrix is efficiently transmitted to the strip, it is advantageous in that the piezoelectric deformation performance is excellent.

The domain has a decay rate ((piezoelectric α-piezoelectric β) calculated from the piezoelectric α at room temperature before heating and the piezoelectric β at room temperature after being held at 85 ° C. for 7 days. / Piezoelectricity α) is preferably 0.1 or less, more preferably 0.05, and particularly preferably 0.
The method for measuring piezoelectricity is not particularly limited, and can be measured by a method appropriately selected according to the purpose. For example, it can be easily measured using a piezoelectric property measuring device (for example, a rheograph). it can.
By suppressing the attenuation factor to 0.1 or less, sufficient piezoelectricity is maintained even when held for a long time under high temperature conditions, and it is suitably used for applications requiring heat resistance. This is advantageous in that it can.

There is no restriction | limiting in particular as content in the said piezoelectric conversion composite material of the said strip, Although it can select suitably according to the objective, 5 mass% or more is preferable.
When the content is outside the preferable numerical range, the piezoelectric conversion ability may not be sufficient.

-Matrix material-
The matrix material preferably includes the biodegradable resin in that it has a low environmental impact at the time of disposal, but is not limited thereto, and can be appropriately selected according to the purpose. Examples include resins other than degradable resins, rubber, thermoplastic elastomers, and the like.
The content of the biodegradable resin in the piezoelectric conversion composite material is not particularly limited and may be appropriately selected depending on the intended purpose. From the viewpoint of discardability, for example, 50 to 100% by mass Is preferable, and 80-100 mass% is more preferable.

There is no restriction | limiting in particular as resin other than the said biodegradable resin, According to the objective, it can select suitably, For example, a thermoplastic resin, a thermosetting resin, a photocurable resin etc. are mentioned, Among these, Thermoplastic resins are preferred. These may be used individually by 1 type and may use 2 or more types together. A plasticizer may be added to a resin other than the biodegradable resin for the purpose of adjusting the flexibility of the piezoelectric conversion composite material.
Specific examples of the resin other than the biodegradable resin include polyvinyl chloride, chlorinated polypropylene, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyvinyl fluoride, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, styrene.・ Acrylonitrile copolymer, acrylonitrile / butadiene / styrene terpolymer, vinyl chloride / vinyl acetate copolymer, acrylic / vinyl chloride copolymer, ethylene / vinyl chloride copolymer, ethylene / vinyl alcohol, chlorinated chloride Vinyl, and the like.

There is no restriction | limiting in particular as said rubber | gum, According to the objective, it can select suitably, For example, natural rubber, a synthetic rubber, etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Specific examples of the rubber include natural rubber, modified natural rubber, grafted natural rubber, cyclized natural rubber, chlorinated natural rubber, styrene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, carboxylated nitrile rubber, nitrile rubber / Chlorinated resin blend, nitrile rubber / EPDM rubber blend, butyl rubber, brominated butyl rubber, chlorinated butyl rubber, ethylene-vinyl acetate rubber, acrylic rubber, ethylene-acrylic rubber, chlorosulfonated polyethylene, chlorinated polyethylene, epichlorohydrophosphorus rubber, epi Examples include chlorohydrin-ethylene oxide rubber, methyl silicone rubber, vinyl-methyl silicone rubber, phenyl-methyl silicone rubber, and fluorinated silicone rubber.

  The thermoplastic elastomer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polystyrene-based thermoplastic elastomers, polyvinyl chloride-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, and polyurethane-based thermoplastic elastomers. Polyester thermoplastic elastomer, polyamide thermoplastic elastomer, vinyl chloride thermoplastic elastomer, fluororubber thermoplastic elastomer, chlorinated polyethylene thermoplastic elastomer, and the like. These may be used individually by 1 type and may use 2 or more types together.

  The matrix material contains a conductive material from the viewpoint of efficiently propagating electric energy converted from vibration energy into the matrix material by the piezoelectric domain formed of the piezoelectric conversion material. preferable.

There is no restriction | limiting in particular as said electroconductive material, According to the objective, it can select suitably, For example, electroconductive fine particles, an electroconductive filler, etc. are mentioned suitably. These may be used individually by 1 type and may use 2 or more types together.
Suitable examples of the conductive fine particles include metal fine particles, semiconductor fine particles, carbon black, fullerene, and carbon nanotubes.
Examples of the metal fine particles include metals such as copper, iron and nickel, and fine particles such as alloys.
Suitable examples of the semiconductor fine particles include metal oxides such as silica and alumina.

There is no restriction | limiting in particular as content in the said matrix material of the said electroconductive material, Although it can select suitably according to the objective, 5-50 mass% is preferable.
When the content is out of the preferable numerical range, the electric energy conversion ability may not be sufficient.

The piezoelectric conversion composite material of the present invention can be suitably used in various fields, but is particularly preferably used as a vibration damping material.
In the piezoelectric conversion composite material of the present invention, the matrix material receives external vibrational energy as strain, and the piezoelectric conversion material that functions as a domain indicating piezoelectricity receives strain of the matrix material as strain. It is converted to electricity and released to the outside as Joule heat. As a result, vibration energy from the outside is efficiently absorbed.

  When the piezoelectric conversion composite material is used as a damping material, when the frequency of the vibration to be damped is ω, the capacitance of the domain exhibiting piezoelectricity is C, and the conductive resistance of the matrix material is R, R ≈1 / ωC is preferable from the viewpoint of maximizing piezoelectricity.

(Method for manufacturing piezoelectric conversion composite material)
As a method for producing the piezoelectric conversion composite material of the present invention, a process as shown in FIG. 3 is preferably exemplified, and includes, for example, a domain formation step and a domain dispersion step, and further appropriately selected as necessary. These steps are included.
In addition, as a manufacturing method of the piezoelectric conversion composite material at the time of using the said polylactic acid as a domain, it is as showing in FIG. Since the polylactic acid is a non-polarizable material, it does not have a polarization component, but since it is an optically active polymer, it is oriented uniaxially only by “stretching treatment” described later. In FIG. 3, “flat plate processing”, “stretching treatment”, and “miniaturization” correspond to the domain formation step, and “dispersion in the matrix” corresponds to the domain dispersion step.

The domain forming step is a step of forming a domain exhibiting piezoelectricity.
The domain forming step is performed by cutting a compacted body made of the piezoelectric conversion material into pieces.

  Examples of the method for forming the molded body include a method of performing a drawing treatment after flat plate processing.

  There is no restriction | limiting in particular as the method of the said flat plate processing, It can select suitably from a well-known method, For example, the method of processing into flat form with a hot press is mentioned.

There is no restriction | limiting in particular as the method of the said extending | stretching process, According to the objective, it can select suitably, For example, uniaxial stretching etc. are mentioned. Examples of the uniaxial stretching method include stretching at a desired stretching ratio with a stretching machine and annealing. In this case, the stretching temperature at the time of stretching is preferably set to about glass transition temperature (Tg) to glass transition temperature (Tg) + 20 ° C. If the stretching temperature is too low, stretching cannot be performed, and if it is too high, the orientation becomes unstable, and bending may occur.
The stretching speed during stretching is preferably set to 10 mm / min to 5000 mm / min. If the stretching speed is too slow, the orientation may decrease, and if it is too fast, it may break. The draw ratio is preferably set to about 4 times. If the draw ratio is too small, the piezoelectricity does not appear, and if it is too large, the shape of the molded product may be deteriorated.
Further, the annealing temperature is preferably set to be equal to or higher than the stretching temperature. If the annealing temperature is too low, annealing does not proceed, and if it is too high, the orientation may be disturbed.

The domain dispersing step is a step of dispersing the strips.
The method for dispersing the strips in the matrix material in the domain dispersion step is not particularly limited and can be appropriately selected for the purpose.However, the matrix material is dissolved or dispersed in the solvent. A method of dispersing the fine pieces and forming a film thereof is preferable. There is no restriction | limiting in particular as said film forming method, According to the objective, it can select suitably.
As described above, the piezoelectric conversion composite material of the present invention is efficiently manufactured.

  Further, as a method for producing a piezoelectric conversion composite material in the case where the polarizable piezoelectric conversion material is used as a domain, a process as shown in FIG. 4 is preferably exemplified. For example, a domain forming step, a domain dispersion step, And other processes appropriately selected as necessary. As will be described later, “application / drying”, “orientation”, “film hardening”, and “miniaturization” in FIG. 4 correspond to the domain forming step, and “dispersion in matrix” is the domain dispersion. Corresponds to the process.

The domain forming step is a step of forming a domain exhibiting piezoelectricity.
The domain forming step is performed by cutting a compacted body made of the piezoelectric conversion material into pieces.

  There is no restriction | limiting in particular as a formation method of the said molded object, According to the objective, it can select suitably, For example, the method of apply | coating the said piezoelectric conversion material, the method of shaping | molding, the method of pressing, etc. are mentioned.

The coating method is not particularly limited and can be appropriately selected from known coating methods according to the purpose. Examples thereof include spin coating, bar coating, kneader coating, curtain coating, blade coating, and the like. Law, etc. The piezoelectric conversion material is preferably applied on a rubbing film. There is no restriction | limiting in particular as a formation method of this rubbing film | membrane, According to the objective, it can select suitably.
A solvent can be used in the application. There is no restriction | limiting in particular as this solvent, According to the objective, it can select suitably, These solvents may be used individually by 1 type, and may use 2 or more types together.

  The molding method is not particularly limited and can be appropriately selected from known molding methods depending on the purpose. For example, molding is compression molding, transfer molding, injection molding, powder molding, rotational molding, Examples thereof include blow molding, injection blow molding, extrusion blow molding, extrusion molding, blow molding, calendar molding, thermoforming, pressure molding, fluid molding, paste molding, vacuum molding, foam molding, and laminate molding.

  There is no restriction | limiting in particular as the method of the said press processing, It can carry out by the method suitably selected from the well-known press processing methods.

The orientation method is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include polling treatment.
The poling treatment is not particularly limited and can be appropriately selected depending on the purpose. For example, the molded body (piezoelectric conversion material) is fixed on a hot plate, and tungsten is placed at an appropriately selected distance from the molded body. This can be done by installing a needle and applying an arbitrary voltage to it. In this case, the temperature of the molded body is preferably maintained at a temperature equal to or higher than the softening point of the molded body.

The domain dispersing step is a step of dispersing the strips.
The method for dispersing the strips in the matrix material in the domain dispersion step can be selected from the same method as in the case where the domain is the polylactic acid.
As described above, the piezoelectric conversion composite material of the present invention is efficiently manufactured.

  Hereinafter, although the Example of this invention is described, this invention is not limited to this Example at all.

(Production Example 1)
-Production of piezoelectric conversion materials-
After flat plate processing was performed using poly-L-lactic acid pellets, stretching was performed.

--- Flat plate processing ---
The poly-L-lactic acid pellets were processed into a plate shape of about 0.1 to 1 mm with a hot press.

--Stretching process--
The flat-processed poly-L-lactic acid is uniaxially stretched 4 times with a stretching machine at a stretching temperature of 80 ° C. and a stretching speed of 100 mm / min, and then annealed at 120 ° C. Got. The piezoelectric conversion material was evaluated for the following attenuation rate.

  The piezoelectricity α of the piezoelectric conversion material at room temperature before heating was measured with Rheograph Solid (manufactured by Toyo Seiki Seisakusho) and found to be 10 pC / N. Further, when the piezoelectric conversion material was allowed to stand for 7 days in a state heated to 85 ° C., the same measurement was performed at room temperature. As a result, the piezoelectric β was 10 pC / N. When the attenuation rate ((piezoelectric α-piezoelectric β) / piezoelectric α) of the piezoelectric conversion material was calculated from the measurement results of the piezoelectric properties α and β, the attenuation rate was 0.

(Example 1)
As the domain exhibiting piezoelectricity, a plate-like poly-L-lactic acid obtained in Production Example 1 was cut into an average of 5 mm length to obtain a chopped filamentary piece. Further, as the matrix material, a material obtained by adding 50 parts by mass of carbon black (Tokai Carbon Co., Ltd., Seast 3HAF) as a conductive material to 100 parts by mass of poly-L-lactic acid and mixing at 170 ° C. for 8 hours is used. did. The matrix material and the thread-like piece were mixed and pressed to obtain a sheet-like piezoelectric conversion composite material (1). The content of the filamentous piece in the piezoelectric conversion composite material (1) is 13%.
The following loss factor was measured for the obtained sheet-like piezoelectric conversion composite material (1).

<Measurement of loss factor>
Regarding the sheet-like piezoelectric composite material (1) obtained as described above, the relationship between the resonance frequency (Hz) and the loss factor was examined according to the cantilever method defined in JIS G0602. The results are shown in FIG. Further, the relationship between the anti-resonance frequency (Hz) and the loss factor was examined according to the central excitation method defined in JIS G0602.
The results are shown in FIG.

(Comparative Example 1)
In Example 1, a sheet material was obtained in the same manner as in Example 1 except that the filamentous piece was not used, and the loss factor was measured for the sheet material. The results are shown in FIG.

  As is clear from FIG. 5, it was found that the sheet-like piezoelectric conversion composite material produced in Example 1 functions as a vibration damping material. Further, from the evaluation results of the attenuation rate, it has been found that these piezoelectric conversion composite materials maintain stable piezoelectricity even when kept for a long time under high temperature conditions.

  The piezoelectric conversion composite material of the present invention can be suitably used for vibration damping materials, soundproof walls, and the like. In addition, it exhibits sufficient piezoelectricity, can be mass-produced at low cost, has excellent handling characteristics, has a low environmental impact during disposal, and can be suitably used for applications that require heat resistance. .

FIG. 1 is a schematic view showing a preferred embodiment in the case where the piezoelectric conversion composite material of the present invention has no polarization component. FIG. 2 is a schematic explanatory view showing a preferred embodiment example in the case where the piezoelectric conversion composite material of the present invention has a polarization component. FIG. 3 is a schematic explanatory view showing a preferred production example of the piezoelectric conversion composite material of the present invention. FIG. 4 is a schematic explanatory view showing an example of manufacturing a film strip in the piezoelectric conversion composite material of the present invention. FIG. 5 is graph data showing the relationship between the resonance frequency (Hz) measured according to the cantilever method and the loss factor, and the relationship between the anti-resonance frequency (Hz) measured according to the central excitation method and the loss factor. .

Explanation of symbols

1 Piezoelectric conversion composite material 5 Membrane strip (formed of non-polarizable material)
10 Membrane strip (formed of polarizable material)
20 matrix

Claims (8)

  A piezoelectric conversion composite material comprising a domain exhibiting piezoelectricity in a matrix material, wherein the domain exhibiting piezoelectricity is formed of a piezoelectric conversion material containing a biodegradable resin.   The piezoelectric conversion composite material according to claim 1, wherein the matrix material includes a biodegradable resin.   The piezoelectric conversion composite material according to claim 1, wherein the biodegradable resin is at least one selected from aliphatic polyester resins.   The piezoelectric conversion composite material according to claim 3, wherein the aliphatic polyester resin is at least one selected from polylactic acid-based aliphatic polyester resins.   The piezoelectric conversion composite material according to claim 4, wherein the polylactic acid-based aliphatic polyester resin is polylactic acid.   The piezoelectric conversion composite material according to any one of claims 1 to 5, wherein the domain exhibiting piezoelectricity is a fine piece formed by cutting a molded body made of a piezoelectric conversion material.   The piezoelectric conversion composite material according to claim 6, wherein the strip is a thread-like piece, and the diameter, length and material of the thread-like piece are substantially the same. The piezoelectric conversion composite material according to claim 6, wherein the strip is a thread-like piece and at least one of a diameter, a length, and a material of the thread-like piece is different.

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