Process for producing articles formed from polylactic acid and articles made therefrom

Patent metadata

Field	Value
Publication number	US-10150232-B2
Application number	US-201715485891-A
Country	US
Kind code	B2
Filing date	Apr 12, 2017
Priority date	Jul 29, 2014
Publication date	Dec 11, 2018
Grant date	Dec 11, 2018

Abstract

PLA polymers that can be expanded into microporous articles having a node and fibril microstructure are provided. The fibrils contain PLA polymer chains oriented with the fibril axis. Additionally, the PLA polymers have an inherent viscosity greater than about 3.8 dL/g and a calculated molecular weight greater than about 150,000 g/mol. The PLA polymer article may be formed by bulk polymerization where the PLA bulk polymer is made into a preform that is subsequently expanded at temperatures above the glass transition temperature and below the melting point of the PLA polymer. In an alternate embodiment, a PLA polymer powder is lubricated, the lubricated polymer is subjected to pressure and compression to form a preform, and the preform is expanded to form a microporous article. Both the preform and the microporous article are formed at temperatures above the glass transition temperature and below the melting point of the PLA polymer.

First claim

What is claimed is:

1. A process for forming a porous article comprising:
expanding a PLA polymer at a temperature above the glass transition temperature of said PLA polymer and below a melting temperature of said PLA polymer to create a porous expanded PLA polymer article comprising a detectable beta crystal phase and nodes and fibrils.

2. The process of claim 1 , wherein said expanding occurs at a temperature from at least about 1° above the glass transition temperature of said PLA polymer to at least about 1° C. below the melt temperature of said PLA polymer.

3. The process of claim 1 , wherein said expanding occurs at a temperature from about 60° C. to about 185° C. to form said porous PLA article.

4. The process of claim 1 , further comprising compressing said porous PLA polymer article at a temperature below said melting temperature of said PLA polymer to form a dense PLA article having a porosity less than about 10%.

5. The process of claim 1 , further comprising adding at least one member selected from the group consisting of a filler material and a coating material to said porous PLA article.

6. The process of claim 1 , further comprising removing residual monomer prior to said expanding below said melt temperature of said PLA polymer.

7. The process of claim 1 , wherein said fibrils comprise polymer chains and said polymer chains are oriented along a fibril axis.

8. The process of claim 1 , wherein said expanded PLA polymer article is in the form of films, rods, tubes, or discs.

9. The process of claim 1 , wherein said porous PLA polymer article has a matrix tensile strength greater than or equal to 110 MPa.

10. The process of claim 1 , wherein said porous PLA polymer article has a modulus greater than or equal to 3000 MPa.

11. The process of claim 1 , wherein said porous PLA polymer article has a porosity greater than about 25%.

12. The process of claim 1 , wherein said PLA polymer has an inherent viscosity greater than about 5 dL/g.

13. The process of claim 12 , wherein said PLA polymer has a molecular weight greater than about 290,000 g/mol.

14. The process of claim 1 , wherein said PLA polymer article has a melt enthalpy greater than about 30 J/g.

15. The process of claim 1 , wherein said PLA polymer comprises at least one comonomer.

16. The process of claim 1 , wherein said PLA polymer comprises poly L-lactic acid (PLLA), poly d-lactic acid (PDLA), poly L-lactide, poly D-lactide, and combinations thereof.

17. A process for forming a microporous article comprising:
lubricating a PLA polymer powder to form a lubricated PLA polymer;
subjecting said lubricated PLA polymer to pressure and to a temperature above the glass transition temperature of said PLA polymer and below a melting temperature of said PLA polymer to form a preform; and
expanding said preform at a temperature below the melt temperature of said PLA polymer to form a porous PLA article having a structure of nodes and fibrils.

18. The process of claim 17 , wherein said subjecting comprises calendering said preform article below said melt temperature.

19. The process of claim 17 , wherein said calendering occurs at a temperature that is about 80° C. or less below said melt temperature.

20. The process of claim 17 , wherein said subjecting step comprises ram extruding said lubricated PLA polymer at a temperature that is below said melt temperature of said PLA polymer.

21. The process of claim 20 , wherein said ram extruding occurs at a temperature that is about 80° C. or less below said melt temperature.

22. The process of claim 17 , further comprising removing said lubricant from said preform prior to said expanding.

23. The process of claim 17 , further comprising compressing said porous PLA article to form a dense article having a porosity of less than about 10%.

24. The process of claim 17 , further comprising adding at least one member selected from the group consisting of a filler material and a coating material to said microporous article.

25. The process of claim 17 , wherein said PLA polymer comprises poly L-lactic acid (PLLA), poly d-lactic acid (PDLA), poly L-lactide, poly D-lactide, and combinations thereof.

26. The process of claim 17 , wherein said PLA polymer comprises at least one comonomer.

27. The process of claim 17 , wherein said porous PLA article has a matrix tensile strength greater than or equal to 110 MPa.

28. The process of claim 17 , wherein said porous PLA article has a matrix modulus greater than or equal to 3000 MPa.

29. The process of claim 17 , wherein said porous PLA article has a porosity greater than about 25%.

30. The process of claim 17 , wherein said PLA polymer has an inherent viscosity greater than about 3.8 dL/g.

31. The process of claim 30 , wherein said PLA polymer has a molecular weight greater than about 190,000 g/mol.

32. The process of claim 17 , wherein said PLA polymer has a melt enthalpy greater than about 30 J/g.

33. The process of claim 17 , wherein said fibrils comprise polymer chains and said polymer chains are oriented along a fibril axis.

34. The process of claim 1 , wherein said nodes comprise a volume of said expanded PLA polymer, and
wherein said fibrils originate and terminate from said nodes.

Assignees

• Gore & Ass

Inventors

• Sbriglia Guy A
• Gore Scott A

Classifications

• B29C43/003 Primary

  characterised by the choice of material · CPC title

• B29C43/24

  Calendering · CPC title

• C08J9/0014

  Use of organic additives · CPC title

• B29C48/022

  characterised by the choice of material · CPC title

• C08J2367/04

  Polyesters derived from hydroxy carboxylic acids, e.g. lactones (C08J2367/06 takes precedence) · CPC title