Foams based on thermoplastic polyurethanes
Expandable thermoplastic polyurethane comprising blowing agent, wherein the Shore hardness of the thermoplastic polyurethane is from A 44 to A 84.
1. A method of making a molded particle foam, the method comprising:
impregnating thermoplastic polyurethane pellets with a blowing agent to form expandable thermoplastic polyurethane beads;
expanding the thermoplastic polyurethane beads; and
fusing the expanded thermoplastic polyurethane beads to one another in a closed mold to form a sole for an article of footwear.
2. The method of claim 1 , wherein the sole comprises a midsole.
3. The method of claim 2 , wherein the midsole consists of the expanded thermoplastic polyurethane beads.
4. The method of claim 2 , wherein the expanded thermoplastic polyurethane beads form the entire midsole.
5. The method of claim 1 , wherein the sole comprises an insole.
6. The method of claim 1 , wherein the expanded thermoplastic polyurethane beads form the entire sole.
7. The method of claim 1 , wherein the expanded thermoplastic polyurethane beads are based on a polyether alcohol.
8. The method of claim 1 , wherein the expanded thermoplastic polyurethane beads are based on a polyester alcohol.
9. The method of claim 1 , wherein the sole comprises a density between 8 and 600 g/l.
10. The method of claim 1 , wherein the expanded thermoplastic polyurethane beads have a diameter between 0.2 mm and 20 mm.
11. The method of claim 10 , wherein the diameter is between 0.5 mm and 15 mm.
12. The method of claim 10 , wherein the diameter is between 1 mm and 12 mm.
13. The method of claim 1 , wherein the expanded thermoplastic polyurethane beads are spherical.
14. The method of claim 1 , wherein the expanded thermoplastic polyurethane beads are cylindrical.
15. The method of claim 1 , wherein the expanded thermoplastic polyurethane beads are elongate.
16. The method of claim 1 , wherein fusing the expanded thermoplastic polyurethane beads to one another in a closed mold to form the sole comprises exposing the expanded thermoplastic polyurethane beads to a temperature between 100° C. and 140° C.
17. The method of claim 16 , wherein exposing the expanded thermoplastic polyurethane beads to a temperature between 100° C. and 140° C. comprises exposing the expanded thermoplastic polyurethane beads to steam.
18. The method of claim 1 , wherein the blowing agent comprises between 0.1% and 40% of the total weight of the pellets.