Biodegradable, industrially compostable, and recyclable injection molded microcellular flexible foams
This document discloses a process for manufacturing recyclable injection molded microcellular foams for use in, footwear components, seating components, protective gear components, and watersport accessories. The process includes the steps of providing a thermoplastic polymer which comprises at least one monomer derived from depolymerized post-consumer plastic, inserting a fluid into a barrel of a molding apparatus. The fluid is introduced under temperature and pressure conditions to produce a super critical fluid. The process further includes mixing the thermoplastic polymer and super critical fluid so as to create a single phase solution, and injecting the single phase solution into a mold of an injection molding machine under gas counter pressure. The process further includes foaming the single phase solution by controlling the head and temperature conditions within the mold.
1. A method for manufacturing a flexible foam, the method comprising:
forming a molten polymer from a thermoplastic masterbatch, the thermoplastic masterbatch comprising one or more recyclable thermoplastic polymers;
mixing a supercritical fluid with 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; 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.
2. The method of claim 1 , wherein the one or more recyclable thermoplastic polymers comprise one or more polyamides or polyamide block copolymers.
3. The method of claim 2 , wherein the one or more polyamides or polyamide block copolymers comprises one or more of polyamide 6, polyamide 6/6, polyamide 12, thermoplastic polyamide (TPA), polyether-block-amide (PEBA), or combinations thereof.
4. The method of claim 1 , wherein at least a portion of the one or more recyclable thermoplastic polymers are derived from depolymerized post-consumer or post-industrial plastic.
5. The method of claim 4 , wherein the depolymerized post-consumer or post-industrial plastic comprises caprolactam.
6. The method of claim 1 , wherein the one or more recyclable thermoplastic polymers do not cross-link during manufacturing of the flexible foam.
7. The method of claim 1 , wherein the supercritical fluid comprises supercritical nitrogen.
8. The method of claim 1 , wherein the supercritical fluid comprises supercritical carbon dioxide.
9. 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.
10. 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.
11. The method of claim 1 , wherein pressurizing the mold cavity comprises pressurizing the mold cavity in the range of about 5 bar to about 50 bar for a length of time between 1 second to 25 seconds with the counterpressure gas.
12. 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.
13. The method of claim 12 , further comprising controlling a temperature of the surface of the mold cavity with a dynamic mold temperature control system that is configured to provide hot and cold thermal cycling.
14. The method of claim 13 , wherein the dynamic mold temperature control system comprises one or more heating elements and one or more cooling elements coupled to the molding apparatus.
15. The method of claim 1 , wherein the flexible foam has a density in a range of about 2 lbs/ft 3 to about 10 lbs/ft 3 .
16. The method of claim 1 , wherein the mold cavity has a shape such that the flexible foam is formed into a shape of a shoe component in the mold cavity.
17. The method of claim 16 , wherein the shoe component is selected from one or more of a shoe sole, a shoe midsole, or a shoe insole.
18. The method of claim 1 , wherein the flexible foam does not comprise cross-linked thermoplastic polymers.
19. The method of claim 18 , wherein the flexible foam comprises thermoplastic polymers that can be depolymerized into monomers using a thermal and/or chemical depolymerization process.
20. The method of claim 19 , wherein the monomers comprise caprolactam.