JPH0575192B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a polymeric piezoelectric material obtained by thermally electrifying a polyester molded article containing an aromatic hydroxycarboxylic acid residue and exhibiting anisotropy when melted. [Prior art and problems] It is well known that polymer ferroelectrics are thermally electrified to obtain electret elements and used in piezoelectric and pyroelectric materials. Various polymeric piezoelectric materials are known, such as polyvinylidene cyanide-vinyl acetate copolymer. These polymeric piezoelectric materials are flexible and can be made into films, so large areas can be easily obtained, and a wide range of applications have been developed because polymers have good moldability, which is not found in inorganic piezoelectric materials. It is considered possible. However, the operating temperature range of these polymeric piezoelectric materials is limited because the piezoelectricity is derived from the higher-order structure of the polymer. At most,
The temperature cannot exceed 140-160℃, and there are restrictions on its use. [Means for Solving the Problems] In view of the above-mentioned problems, the present inventors conducted intensive research to develop a polymer piezoelectric material that can be used in a wide temperature range and can be easily converted into a thermoelectret. Focusing on the fact that polymers that sometimes exhibit anisotropy, that is, liquid crystal polymers, have easy movement of polarization orientation, we found that polymers that have aromatic hydroxycarboxylic acid residues in their molecular chains exhibit dipole anisotropy. The present invention has been completed based on the discovery that the present invention has the following properties. That is, the present invention provides a molded article of a polyester containing an aromatic hydroxycarboxylic acid residue that exhibits anisotropy when melted and/or a polyester that partially contains a polyester that exhibits anisotropy when melted in the same molecular chain. This invention relates to a polymer piezoelectric material obtained by electrification. The polyester used in the present invention is a thermoplastic melt processable polymer composition that exhibits optical anisotropy when melted, and is generally classified as a thermotropic liquid crystal polymer. A polymer that forms such an anisotropic melt phase has a property in which the polymer molecular chains are regularly arranged in parallel in a molten state. The state in which the molecules are arranged in this way is often called the liquid crystal state. Such polymers are generally elongated, flat, and made from monomers that are fairly rigid along the long axis of the molecule and have multiple chain extensions, usually in either coaxial or parallel relationships. Manufactured. The nature of the anisotropic melt phase can be confirmed by conventional polarization testing using crossed polarizers.
More specifically, the confirmation of the anisotropic melt phase is based on the Leitz
This can be done by observing a sample placed on a Leitz hot stage under a nitrogen atmosphere at 40x magnification using a polarizing microscope. The above polymer is optically anisotropic. That is, it transmits light when examined between orthogonal polarizers. If the sample is optically anisotropic, polarized light will pass through it even if it is at rest. In the present invention, the polyester exhibiting anisotropy when melted is characterized in that it contains aromatic hydroxycarboxylic acid residues and their aromatic substituted derivative residues, and the hydroxyl group and the carboxylic acid group are attached to the aromatic ring. Direct bonding is preferred, and the hydroxy group and carboxylic acid group may be on the same aromatic ring or on different rings, but both must be in the same molecule of the aromatic ring compound. is necessary. It is particularly preferred that the aromatic hydroxycarboxylic acid residue consists of one or more selected from hydroxybenzoic acid residues, hydroxynaphthoic acid residues, and aromatic substituted derivative residues thereof. In addition, the aromatic substituted derivative residue consists of a substituent and a substitution position that give anisotropy to the intramolecular dipole moment of the hydroxycarboxylic acid compound, and the aromatic substituted derivative residue is an aromatic substituted derivative in which the hydroxyl group and the carboxylic acid group are bonded. Those consisting of substituents and substitution positions that give dipole moment anisotropy along the line direction connecting carbons on the group ring are preferable, and specifically those represented by the following general formulas () to () are preferable. preferable.

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〔Effect of the invention〕

A molded article of the present invention of a polyester containing an aromatic hydroxycarboxylic acid residue that exhibits anisotropy when melted and/or a polyester partially containing a polyester that exhibits anisotropy when melted in the same molecular chain is made into a thermoelectret. The polymer piezoelectric material obtained by this method exhibits high heat resistance and stability, and because the molecular chains have rigidity, the molecules move extremely easily when melted, and the response to thermal electrification is high. Therefore, the polymeric piezoelectric material obtained by the present invention has a wide range of uses, and can be used in environments of 150°C or higher, where it is difficult to use ordinary ferroelectric polymeric materials, and can be used as a heat-resistant piezoelectric material. It has application fields such as pressure elements, movable elements, acoustic transducers, ultrasonic transducers, and medical transducers, and as a pyroelectric material, it has various application fields such as infrared sensors and radiation sensors. These applied fields are detailed in general books such as ``Fine Electronics and Highly Functional Materials'' edited by Higaki, published by CMC Co., Ltd. (June 1981), p. 168. [Examples] The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples. Example 1 1261 parts by weight of 4-acetoxybenzoic acid and 691 parts by weight of 6-acetoxy-2-naphthoic acid were charged into a reactor equipped with a stirrer, a nitrogen introduction pipe and a distillation pipe,
The mixture was heated to 250°C under a stream of nitrogen. While distilling acetic acid from the reactor, at 250℃ for 3 hours,
Next, the mixture was vigorously stirred at 280°C for 2 hours. Furthermore, after increasing the temperature to 320 °C and stopping the introduction of nitrogen,
Gradually reduce the pressure in the reactor and reduce the pressure to 0.1mm after 20 minutes.
Hg and stirred at this temperature and pressure for 1 hour. The resulting polymer had an intrinsic viscosity of 5.4, measured in pentafluorophenol at 60° C. at a concentration of 0.1% by weight. This polymer has the following structural units.

[Chemical formula] A 20μ thick film was made from this polymer using a T-die extruder. The extruder was heated to 300℃.
The T-die was set at 290°C, and the film stretching ratio was 1/10. Both sides of the film were deposited with silver, heated at 260° C., applied a DC voltage of 100 kV/cm for 60 minutes, and then rapidly cooled. The elongation piezoelectric constant d ₃₁ of the obtained test piece was 8.5×10 ⁻⁸ CGS _esu . The pyroelectric constant was 5.7×10 ^-10 C/cm. 160 similar measurements
When carried out under heating at 0.degree. C., _d31 was 10.times.10.sup. ^-8 CGS _esu . Example 2 Polyethylene terephthalate (intrinsic viscosity 0.36)
138.2 parts by weight of polyester prepolymerized according to Example 1 (intrinsic viscosity 0.77, polymerization conditions 260°C,
3 hours), and the reaction was continued in the same reactor and vigorously stirred at 280°C for 4 hours. After further increasing the temperature to 320℃ and stopping the introduction of nitrogen,
Gradually reduce the pressure in the reactor and reduce the pressure to 0.1mm after 15 minutes.
Hg and stirred at this temperature and pressure for 1 hour. The resulting polymer had an intrinsic viscosity of 2.9, measured in pentafluorophenol at a concentration of 0.1% by weight at 60°C. The composition of the obtained polymer was 40 mol% of polyethylene terephthalate and 60 mol% of hydroxybenzoic acid and hydroxynaphthoic acid. A test piece was obtained in the same manner as in Example 1,
The material was electrified by applying a DC voltage of 100 kV/cm for 60 minutes under heating at 200° C., and the piezoelectric constant was measured, and d ₃₁ was 9.1×10 ⁻⁸ CGS _esu . The pyroelectric constant is
It was 6.2×10 ^-10 C/cm〓. Similar measurements at 160℃
_d31 was 12×10 ^-8 CGS _esu . Example 3 900 parts by weight of 4-acetoxybenzoic acid, 431 parts by weight of 4-acetoxy-3-chlorobenzoic acid, and 690 parts by weight of 6-acetoxy-2-naphthoic acid were mixed with a stirrer,
The mixture was charged into a reactor equipped with a nitrogen inlet tube and a distillation tube, and heated to 250° C. under a nitrogen stream.
The mixture was vigorously stirred at 250°C for 3 hours and then at 280°C for 2 hours while distilling acetic acid from the reactor. Furthermore,
After raising the temperature to 320℃ and stopping the introduction of nitrogen, the pressure inside the reactor was gradually reduced and the pressure was increased after 20 minutes.
The temperature was lowered to 0.1 mmHg, and the mixture was stirred for 1 hour at this temperature and pressure. The resulting polymer had an intrinsic viscosity of 5.0, measured in pentafluorophenol at 60° C. at a concentration of 0.1% by weight. 100kV/heated at 220℃ in the same manner as in Example 1.
When a DC voltage of cm was applied for 60 minutes to generate an electret and the piezoelectric constant was measured, _d31 was 8.8×
It was 10 ^-8 CGS _esu . The pyroelectric constant is 5.9×10 ^-10 C/
It was cm〓. Comparative Example 1 166 parts by weight of terephthalic acid, 166 parts by weight of isophthalic acid, and 250 parts by weight of diacetoxymethylhydroquinone were charged into a reactor equipped with a stirrer, a nitrogen introduction tube, and a distillation tube, and the mixture was heated to 260 parts by weight under a nitrogen stream. ℃
heated to. While distilling acetic acid from the reactor,
The mixture was stirred vigorously at 260°C for 2.5 hours and then at 280°C for 3 hours. Further, the temperature was raised to 320°C, and after stopping the introduction of nitrogen, the pressure inside the reactor was gradually reduced to 0.1 mmHg after 15 minutes.
Stir for hours. The logarithmic viscosity of this polymer is tetrachloroethane/
It was measured at 0.5% by weight using a 1/1 mixed solvent of phenol and found to be 0.87. This polymer was thermally electrified in the same manner as in Example 3, and the piezoelectric constant _d31 was measured to be 9.2×10 ^-10 CGS _esu
obtained the value of Example 4 The polymer obtained in Example 1 was heated using a heating roll.
Zircon/lead titanate while heating to 280℃
PbZrO ₃ -PbTiO ₃ ceramic powder was gradually added to the resulting composite in an amount of 30% by volume and mixed uniformly, followed by hot pressing to obtain a film with a thickness of 50 μm. A test piece was obtained from the obtained film in the same manner as in Example 1, and heated at 220°C at 200kV/cm.
When the piezoelectric constant _d31 was measured by applying a DC electric field of 60 minutes for electret processing, it was found to be 2.6×
It was 10 ^-7 CGS _esu . Example 5 A film having a thickness of 50 μm was obtained from the polymer obtained in Example 2 in the same manner as in Example 4. At this time, the heating roll was heated to 220°C. Under heating at 220℃, 200kV/
A DC electric field of cm was applied for 60 minutes to perform electret processing, and a piezoelectric constant d ₃₁ of 2.9×10 ⁻⁷ CGS _esu was obtained. Example 6 The polymer obtained in Example 1 was hot pressed.
Heat to 280℃, sandwich copper plates on both sides and heat at 280℃.
A DC electric field of 100 kV/cm was applied for 60 minutes for rapid cooling.
The obtained film was freeze-pulverized at -60°C to obtain an acicular powder. Polyacetal (polyplastics)
Co., Ltd., trade name "Dyuracon M-90") was kneaded using rolls heated to 180°C, and 40% by volume of the previously obtained acicular powder was added and mixed uniformly. The obtained composite was formed into a 50μ film using a hot press, and subjected to electret treatment at 100°C for 60 minutes at 200kV/cm in the same manner as in Example 1, and the piezoelectric constant _d31 was measured to be 2.2×10 ^-8 It was CGS _esu . Incidentally, polyacetal under similar measurement conditions is 7.7×10 ^-10 CGS _esu
showed that. Example 7 A polyvinylidene fluoride resin (KF-1100 manufactured by Kureha Chemical Co., Ltd.) containing 50% by volume of the electret-treated acicular powder obtained in Example 6 was prepared in the same manner as in Example 6 using a heated roll. After that, the test piece
When the piezoelectric constant _d31 was measured after electret treatment at 100℃, 200kV/cm, 60 minutes, it was 1.5×
It was 10 ^-7 CGS _esu . Incidentally, the d ₃₁ of polyvinylidene fluoride resin alone was 1.0×10 ⁻⁷ CGS _esu . Example 8 The polymer obtained in Example 1 was frozen and ground at -60°C to obtain an acicular powder. Polybutylene terephthalate (Polyplastics Co., Ltd., trade name "Jyuranetx 2002") was kneaded with a roll while being heated to 230°C, and 50% by volume of the previously obtained acicular powder was added and mixed uniformly. A 50μ test piece was prepared using a hot press, and the same procedure as in Example 1 was carried out at 200°C and 200kV/
cm, piezoelectric constant after 60 min electret treatment
When _d31 was measured, it was 4.0×10 ^-8 CGS _esu . Incidentally, the d ₃₁ of polybutylene terephthalate is 8.0.
It was ×10 ^-10 CGS _esu . Example 9 An acicular powder was prepared from the polymer obtained in Example 2 in the same manner as in Example 8, and a test piece was prepared in the same manner and subjected to electret treatment to measure the piezoelectric _constant . was 3.8×10 ^-8 CGS _esu .

Claims (1)

[Scope of Claims] 1. A polyester containing an aromatic hydroxycarboxylic acid residue and exhibiting anisotropy when melted, and/or a polyester molded article partially containing a polyester exhibiting anisotropy when melting in the same molecular chain. A polymer piezoelectric material obtained by thermally electrifying. 2. Claim 1, wherein the aromatic hydroxycarboxylic acid residue is one or more compounds selected from hydroxybenzoic acid residues, hydroxynaphthoic acid residues, and aromatic substituted derivative residues thereof. polymer piezoelectric materials. 3 A polyester containing an aromatic hydroxycarboxylic acid residue and showing anisotropy when melted partially in the same molecular chain is a polyester that shows anisotropy when melting, other aromatic polyesters, and polycarbonates. The polymeric piezoelectric material according to claim 1, which is a molded article made of a copolymer with one or more selected from polyether sulfone, polyacrylate, and polyalkylene terephthalate. 4 A polyester containing an aromatic hydroxycarboxylic acid residue and showing anisotropy when melted and/or a polyester partially containing an ester showing anisotropy when melting in the same molecular chain can be used in other thermoplastic polymers. The polymeric piezoelectric material according to claim 1, which is a molded article. 5. The polymeric piezoelectric material according to claim 2, wherein the substituent of the aromatic substituted derivative residue consists of a substituent and a substituent position that impart anisotropy to the intramolecular dipole moment of the hydroxycarboxylic acid compound. 6 Substituents and substitution positions of aromatic substituted derivative residues that give dipole moment anisotropy along the line direction connecting the carbons on the aromatic ring to which the hydroxyl group and the carboxylic acid group are bonded. A resin molded article according to claim 2 selected from the following. 7. The resin molded article according to claim 2, wherein the aromatic hydroxycarboxylic acid residue is one or more selected from the following general formulas () to (). [Formula] [Formula _] [Formula] [ _Formula ] [Formula] [Formula _] [Formula] (However _, in the formula, X _{1 ,} They exist separated by a center line that is perpendicular to the center of the line connecting the carbon atoms on the aromatic ring to which the group and the carboxylic acid group are bonded, and each group consists of one or more substituents selected from substituents with different dipole moments. Two or more types, and the same group does not include those with different dipole moment directions. The unsubstituted moiety in each group represents hydrogen.) 8 The substituent is a cyano group, a nitro group, an aldehyde group, a carboxylic acid group. One or more types selected from ester, carboxylic acid group, hydroxy group, hydrogen, halogen compound, amino group, imino group, azo group, alkoxy group, alkyl group, phenyl group, acyl group, sulfoxy group, and sulfide group A polymeric piezoelectric material according to any one of claims 5 to 7. 9. Claims in which the substituent is one or more selected from hydrogen, cyano group, nitro group, acetoxy group, chloro, bromine, phenyl group, alkyl group, methoxy group, amino group, and alkyl-substituted amino group The polymer piezoelectric material according to any one of items 5 to 7. 10. The polymeric piezoelectric material according to claim 1, wherein the polyester exhibiting anisotropy when melted has a molecular weight of 2,000 to 50,000. 11 A polyester that exhibits anisotropy when melted and contains an aromatic hydroxycarboxylic acid residue that undergoes thermal electrification, and/or a molded article of polyester that partially contains a polyester that exhibits anisotropy when melted in the same molecular chain. The polymeric piezoelectric material according to claim 1, which is a molded article containing a ferroelectric compound therein. 12. The polymeric piezoelectric material according to claim 11, wherein the ferroelectric compound is an organic compound. 13. The polymeric piezoelectric material according to claim 11, wherein the ferroelectric compound is an inorganic compound. 14 Inorganic compounds include crystal, lead zirconate titanate, potassium dihydrogen phosphate, barium titanate, lead titanate, lead niobate, lithium niobate, lithium tantalate, barium strontium niobate, Pb (B ₁ B ₂ ) _O3 and _PbTiO3・
PbZrO ₃・Pb(B ₁・B ₂ )O ₃ (However, B ₁ is Mg, Co,
It represents Ni, Mn or Zn, and B ₂ represents Nb, Ta, Sb or W. 14. The polymeric piezoelectric material according to claim 13, which is one or more compounds selected from the following. 15. The polymeric piezoelectric material according to claim 12, wherein the organic compound is Rothsiel's salt or triglycine sulfate. 16. The polymeric piezoelectric material according to claim 12, wherein the organic compound is a polymeric ferroelectric material. 17. The polymeric piezoelectric material according to claim 12, wherein the organic compound is a low molecular weight ferroelectric liquid crystal compound. 18 Polymer ferroelectric material is vinylidene fluoride, 3
The polymeric piezoelectric material according to claim 16, which is one or more selected from ethylene fluoride, vinylidene cyanide, and chloroacrylonitrile. 19. The polymeric piezoelectric material according to claim 1, wherein the polymeric piezoelectric material is in the form of a sheet or film. 20. The polymeric piezoelectric material according to claim 1, wherein the polymeric piezoelectric material is in the form of powder or fiber. 21. The polymeric piezoelectric material according to claim 19, wherein both sides of the film-like polymeric piezoelectric material are treated with conductive thin films. 22. The polymeric piezoelectric material according to claim 1, wherein thermal electrification is performed by applying direct current or by applying both direct current and alternating current. 23. The polymeric piezoelectric material according to claim 1, wherein the thermoelectretted polymeric piezoelectric material is in the form of fibers. 24. The polymeric piezoelectric material according to claim 1, wherein the thermoelectretted polymeric piezoelectric material is in the form of powder and/or short fibers. 25. The polymeric piezoelectric material according to claim 24, wherein the thermoelectretted powdered and/or short fiber polymeric piezoelectric material is dispersed in another resin. 26. The polymeric piezoelectric material according to claim 24, wherein the thermoelectretted polymeric piezoelectric material is dispersed in a thermosetting resin. 27. The polymeric piezoelectric material according to claim 24, wherein the thermoelectretted polymeric piezoelectric material is dispersed in a thermoplastic resin. 28. The polymeric piezoelectric material according to claim 27, wherein the thermoplastic resin has a melting point lower than the melting point of the thermoelectrifying resin. 29. The thermoplastic resin according to claim 27, wherein the thermoplastic resin is one or more selected from polyacetal, polybutylene terephthalate, polyethylene terephthalate, vinylidene fluoride, ethylene trifluoride, vinylidene cyanide, and chloroacrylonitrile. Polymer piezoelectric material. 30. The polymeric piezoelectric material according to claim 25, wherein the resin composite in which the thermoelectrified resin is dispersed is further subjected to thermoelectret treatment.