Polymeric piezoelectric material

• US 5,298,602 A
• Filed: 01/28/1993
• Issued: 03/29/1994
• Est. Priority Date: 11/06/1992
• Status: Expired due to Term

• Current Assignee: Takiron Company Limited (Itochu Corporation)
• Original Assignee: Takiron Company Limited (Itochu Corporation)
• Inventors: Shikinami, Yasuo, Hata, Kunihiro
• Primary Examiner(s): Kight, III, John
• Assistant Examiner(s): Dodson, Shelley A.
• Application Number:
  US08/010,165
• Time in Patent Office: 425 Days
• Field of Search: 29/25.35, 29/594, 29/595, 252/62.9, 528/361
• US Class Current: 528/361
• CPC Class Codes: A61F 2/28 Bones joints A61F2/30
• CPC Class Codes: A61F 2002/2821 Bone stimulation by electromagnetic fields or electric current for enhancing ossification
• CPC Class Codes: A61F 2002/30087 piezoelectric
• CPC Class Codes: A61L 31/06 obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds A61L31/041 takes precedence
• CPC Class Codes: A61L 31/14 Materials characterised by their function or physical properties , e.g. injectable or lubricating compositions, shape-memory materials, surface modified materials
• CPC Class Codes: C08L 67/04 Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence
• CPC Class Codes: H04R 17/025 using a piezoelectric polymer
• CPC Class Codes: H10N 30/857 Macromolecular compositions
• CPC Class Codes: Y10S 623/923 Bone
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 Acoustic transducer
• CPC Class Codes: Y10T 29/49007 Indicating transducer

Abstract

A polymeric piezoelectric material including a polylactic acid molded article having been uniaxially drawn to an extent causing no fibrillation. The piezoelectric material exhibits piezoelectric properties equal to or higher than those of electret type or polypeptide type piezoelectric materials while having high enough mechanical strength to be processed into various articles ranging from films to profiles depending on the end use.

Claims

1. A polymeric piezoelectric material comprising a polylactic acid molded article having been uniaxially drawn to an extent causing no fibrillation.

2. A polymeric piezoelectric material as claimed in claim 1, wherein said polylactic acid molded article has a piezoelectric constant -d'"'"'₁₄ of from 8 to 13 pC/N and a piezoelectric constant -e'"'"'₁₄ of from 10 to 20 mC/m².

3. A polymeric piezoelectric material as claimed in claim 1, wherein said polylactic acid molded article has (a) a thickness direction and (b) a drawing direction, and the drawing direction forms an angle other than 90°

with the thickness direction.

4. A polymeric piezoelectric material as claimed in claim 1, wherein said polylactic acid molded article is a film.

5. A polymeric piezoelectric material as claimed in claim 4, wherein said film has (a) an axial direction which connects two ends of the film which are to be fixed and (b) a drawing direction, and the drawing direction forms an angle other than 90°

with the axial direction.

6. A polymeric piezoelectric material as claimed in claim 1, wherein said polylactic acid molded article is a rod.

7. A polymeric piezoelectric material as claimed in claim 6, wherein said rod has (a) an axial direction which connects two ends of the rod and (b) a drawing direction, and the drawing direction forms an angle other than 90°

with the axial direction.

8. A polymeric piezoelectric material as claimed in claim 1, wherein said polylactic acid molded article is a plate.

9. A polymeric piezoelectric material as claimed in claim 8, wherein said plate has (a) an axial direction which connects two ends of the plate and (b) a drawing direction, and the drawing direction forms an angle other than 90°

with the axial direction.

10. A polymeric piezoelectric material as claimed in claim 1, wherein said polylactic acid molded article has a draw ratio of from 3 to 6.

11. A polymeric piezoelectric material as claimed in claim 10, wherein said polylactic acid molded article has a draw ratio of from 4 to 5.

12. A polymeric piezoelectric material as claimed in claim 1, wherein said polylactic acid molded article comprises a homopolymer of L- and D-lactic acid.

13. A polymeric piezoelectric material as claimed in claim 1, wherein said polylactic acid molded article comprises polylactic acid having a viscosity-average molecular weight of from 50,000 to 1,000,000.

14. A polymeric piezoelectric material as claimed in claim 1, wherein the polylactic acid molded article is formed by extrusion at a temperature between the melting point of polylactic acid and 220°

C.

15. A polymeric piezoelectric material as claimed in claim 1, wherein the polylactic acid molded article is drawn at a temperature of from 60 to 180°

C.

16. A polymeric piezoelectric material as claimed in claim 1, wherein the polylactic acid molded article is a film having a thickness ranging from 50 to 500 μ

m.

17. A method for treating a fractured bone, comprising

(A) forming a polymeric piezoelectric material comprising a polylactic acid film having been uniaxially drawn to an extent causing no fibrillation,

wherein the film has a piezoelectric constant -d'"'"'₁₄ of from 8 to 13 pC/N and a piezoelectric constant -e'"'"'₁₄ of from 10 to 20 mC/m², and

wherein the film has (a) an axial direction which connects two ends of the film which are to be fixed and (b) a drawing direction, and the drawing direction forms an angle other than 90°

with the axial direction, and

(B) applying the film to a bone having a fracture part, with said two ends of the film which are to be fixed being fixed near the fractured part for acceleration of ossification.

18. A method of using a polymeric piezoelectric material, comprising using said material as a piezoelectric element of an ultrasonic transducer of an ultrasonographic device,

wherein the material comprises a polylactic acid molded article having been uniaxially drawn to an extent causing no fibrillation,

wherein the polylactic acid molded article has a piezoelectric constant -d'"'"'₁₄ of from 8 to 13 pC/N and a piezoelectric constant -e'"'"'₁₄ of from 10 to 20 mC/m², and

wherein the polylactic acid molded article has (a) a thickness direction and (b) a drawing direction, and the drawing direction forms an angle other than 90°

with the thickness direction.

19. A method of using a polymeric piezoelectric material, comprising using said material as a piezoelectric element of an ultrasonic probe of an ultrasonic flaw detector,

wherein the material comprises a polylactic acid molded article having been uniaxially drawn to an extent causing no fibrillation,

wherein the polylactic acid molded article has a piezoelectric constant -d'"'"'₁₄ of from 8 to 13 pC/N and a piezoelectric constant -e'"'"'₁₄ of from 10 to 20 mC/m², and

wherein the polylactic acid molded article has (a) a thickness direction and (b) a drawing direction, and the drawing direction forms an angle other than 90°

with the thickness direction.