Biodegradable and industrially compostable injection molded microcellular flexible foams, and a method of manufacturing the same

1. A method for manufacturing a flexible foam, the method comprising:

forming a molten polymer from a biodegradable thermoplastic masterbatch, the biodegradable thermoplastic masterbatch comprising one or more thermoplastic biopolymers;

dissolving a supercritical fluid in the molten polymer to create a single-phase solution;

introducing the single-phase solution into a mold cavity of a molding apparatus, the molding apparatus having at least one pressure sensor for sensing a pressure in the molding apparatus;

foaming the single-phase solution in the mold cavity by allowing the supercritical fluid to come out of solution, thereby forming a flexible foam;

applying a pressure to the single-phase solution and maintaining the pressure prior to introducing the single-phase solution into the mold cavity to prevent premature foaming of the single-phase solution; and

pressurizing the mold cavity with a counterpressure gas during foaming of the single-phase solution, wherein a dosing amount and hold time of the counterpressure gas in the mold cavity is controlled by a computer-controller that receives data from the at least one pressure sensor,

wherein the biodegradable thermoplastic masterbatch does not include ethylene vinyl acetate, and

wherein the flexible foam is non-crosslinked.

2. The method of claim 1 , wherein the one or more thermoplastic biopolymers comprise one or more of polylactic acid, poly(butylene adipate-co-terephthalate), polycaprolactone, polyhydroxy alkanoate, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate, or combinations thereof.

3. The method of claim 1 , wherein the one or more thermoplastic biopolymers are selected from the group consisting of polylactic acid, poly(butylene adipate-co-terephthalate), polycaprolactone, polyhydroxy alkanoate, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate, and combinations thereof.

4. The method of claim 1 , wherein the one or more thermoplastic biopolymers comprise aliphatic and/or aliphatic-aromatic co-polyester biopolymers.

5. The method of claim 1 , wherein the one or more thermoplastic biopolymers are produced from plant-derived feedstocks.

6. The method of claim 1 , wherein the supercritical fluid comprises supercritical nitrogen.

7. The method of claim 1 , wherein the supercritical fluid comprises supercritical carbon dioxide.

8. The method of claim 1 , wherein pressurizing the mold cavity with the counterpressure gas prevents gas bubbles from breaking through a surface of the flexible foam during foaming of the single-phase solution and allows a smooth skin to form on the surface of the flexible foam.

9. The method of claim 1 , further comprising controlling a temperature of the molding apparatus using a dynamic mold temperature control.

10. The method of claim 1 , wherein the supercritical fluid is dissolved in the molten polymer in a barrel of the molding apparatus, the barrel having a screw for conveying the single-phase solution toward the mold cavity.

11. The method of claim 10 , wherein the barrel of the molding apparatus and the mold cavity are connected by a closeable connection.

12. The method of claim 11 , wherein the closeable connection comprises a shutoff nozzle.

13. The method of claim 11 , wherein the closeable connection is in a closed state while the pressure is applied to the single-phase solution.

14. The method of claim 1 , wherein the flexible foam is biodegradable and/or industrially compostable.

15. The method of claim 14 , wherein the flexible foam is industrially compostable at a temperature between 55° C. and 60° C.

16. The method of claim 1 , wherein introducing the single-phase solution into the mold cavity of a molding apparatus comprises contacting a surface of the mold cavity with the single-phase solution.

17. The method of claim 16 , further comprising controlling a temperature of the surface of the mold cavity with a dynamic mold temperature control system.

18. The method of claim 1 , wherein the flexible foam is entirely biodegradable.

19. The method of claim 1 , wherein the one or more biopolymers comprises poly(butylene adipate-co-terephthalate).

20. The method of claim 1 , wherein the supercritical fluid is introduced at a pressure in the range of about 150 bar to about 300 bar and at a temperature in the range of about 150° C. to about 350° C.

21. The method of claim 1 , wherein the mold cavity is pressurized by the counterpressure gas at a pressure in the range of about 5 bar to about 50 bar for a length of time between 1 second to 25 seconds.

22. A method for manufacturing a biodegradable and/or industrially compostable non-crosslinked flexible foam, the method comprising:

forming a molten polymer from a thermoplastic masterbatch comprising a poly(butylene adipate-co-terephthalate) in a barrel of a molding apparatus, wherein the thermoplastic masterbatch does not include ethylene vinyl acetate;

introducing a supercritical fluid into the barrel of the molding apparatus at a pressure in the range of about 150 bar to about 300 bar and at a temperature in the range of about 150° C. to about 350° C., and mixing the supercritical fluid in the molten polymer to create a single-phase solution;

introducing the single-phase solution into a mold cavity of the molding apparatus, the molding apparatus having at least one pressure sensor for sensing a pressure in the molding apparatus;

pressurizing the mold cavity at a pressure in the range of about 5 bar to about 50 bar for a length of time between 1 second to 25 seconds with a counterpressure gas, wherein a dosing amount and hold time of the counterpressure gas in the mold cavity is controlled by a computer-controller that receives data from the at least one pressure sensor; and

foaming the single-phase solution in the mold cavity by releasing the counterpressure gas and allowing the supercritical fluid to come out of solution, thereby forming a flexible foam.