Ultrafine polyactic acid fibers and fiber structure, and process for their production

• US 20070172651A1
• Filed: 03/03/2005
• Published: 07/26/2007
• Est. Priority Date: 03/16/2004
• Status: Abandoned Application

• Current Assignee: Teijin Limited
• Original Assignee: Teijin Limited
• Inventors: Miyoshi, Takanori, Toyohara, Kiyotsuna, Minematsu, Hiroyoshi
• Application Number:
  US10/592,760
• Publication Number:
  US 20070172651A1
• Time in Patent Office: Days
• US Class Current: 428/373
• CPC Class Codes: D01D 5/0038 the fibre formed by solvent evaporation, i.e. dry electro-spinning
• CPC Class Codes: D01F 6/625 derived from hydroxy-carboxylic acids, e.g. lactones
• CPC Class Codes: D01F 6/84 from copolyesters
• CPC Class Codes: Y10T 428/2929 Bicomponent, conjugate, composite or collateral fibers or filaments [i.e., coextruded sheath-core or side-by-side type]

Abstract

A fiber structure is obtained by spinning of a solution of an L-lactic acid condensate and a D-lactic acid condensate by electrospinning. It is possible to provide a fiber structure comprising fibers with extremely small fiber diameters, as well as excellent heat resistance and biodegradability.

Claims

1. Ultrafine polylactic acid fibers comprising as the main constituent component a polylactic acid component with a melting point of 190°

C. or higher, with a mean fiber diameter of no greater than 10 μ

m and fiber lengths of 20 μ

m or greater.

2. Fibers according to claim 1, which contain substantially no constituent component with a melting point of below 190°

C.

3. Fibers according to claim 1, having depressions with diameters of 0.01-1 μ

m on the fiber surfaces, the depressions constituting 10-95% of the fiber surfaces.

4. Fibers according to claim 1, wherein the polylactic acid component is a blend of a condensate with at least 80 mol % L-lactic acid based on the total repeating units and a condensate with at least 80 mol % D-lactic acid based on the total repeating units.

5. Fibers according to claim 4, wherein the weight ratio of the L-lactic acid condensate and the D-lactic acid condensate is (6:

4)-(4;

6).

6. A fiber structure comprising at least ultrafine polylactic acid fibers according to claim 1.

7. A fiber structure according to claim 6, wherein the fibers forming the fiber structure have a mean diameter of no greater than 10 μ

m and contain substantially no fibers with fiber lengths of less than 20 μ

m.

8. A production process for a fiber structure, which includes a stage wherein a condensate with at least 80 mol % L-lactic acid based on the total repeating units and a condensate with at least 80 mol % D-lactic acid based on the total repeating units are combined in a weight ratio of (6:

4)-(4;

6) and then dissolved in a solvent to produce a solution, a stage wherein said solution is spun by an electrospinning method, and a stage wherein a fiber structure is accumulated on a collecting plate by said spinning.

9. A production process according to claim 8, wherein the solvent is a volatile solvent.

10. A production process according to claim 8, wherein the relative humidity is in the range of 20-80% RH between the nozzle and collecting plate where the filamentous substance is formed in the stage of spinning by electrospinning.

11. A production process for a fiber structure which includes a stage wherein a condensate with at least 80 mol % L-lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage wherein a condensate with at least 80 mol % D-lactic acid based on the total repeating units is dissolved in a solvent to produce a solution, a stage in which the two solutions are mixed in a weight ratio of (6:

4)-(4;

6), a stage wherein said mixed solution is spun by an electrospinning method, and a stage wherein a fiber structure is accumulated on a collecting board by said spinning.

12. A production process according to claim 11, wherein the solvent is a volatile solvent.

13. A production process according to claim 12, wherein the volatile solvent is at least one selected from the group consisting of methylene chloride, chloroform, dichloroethane, tetrachloroethane, trichloroethane, dibromomethane, bromoform, tetrahydrofuran and 1,4-dioxane.

14. A production process according to claim 11, wherein the relative humidity is in the range of 20-80% RH between the nozzle and collecting plate where the filamentous substance is formed in the stage of spinning by electrospinning.