Foams based on thermoplastic polyurethanes

Abstract

Expandable thermoplastic polyurethane comprising blowing agent, wherein the Shore hardness of the thermoplastic polyurethane is from A 44 to A 84.

Claims

1. A method of making a sole for an article of footwear, the method comprising: expanding thermoplastic polyurethane beads; and exposing the expanded thermoplastic polyurethane beads to a temperature between 100° C. and 140° C. in a closed mold, wherein the expanded thermoplastic polyurethane beads are fused to one another in the closed mold to form the sole.

2. The method of claim 1, 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 at a temperature between 100° C. and 140° C.

3. The method of claim 1, wherein the expanded thermoplastic polyurethane beads have a density between 5 g/l and 600 g/l.

4. The method of claim 1, wherein the expanded thermoplastic polyurethane beads have a diameter between 0.2 mm and 20 mm.

5. The method of claim 4, wherein the diameter is between 0.5 mm and 15 mm.

6. The method of claim 4, wherein the diameter is between 1 mm and 12 mm.

7. The method of claim 1, wherein the sole comprises a midsole.

8. The method of claim 1, wherein the expanded thermoplastic polyurethane beads are spherical.

9. The method of claim 1, wherein the expanded thermoplastic polyurethane beads are based on a polyether alcohol or a polyester alcohol.

10. A method of making a sole for an article of footwear, the method comprising: mixing thermoplastic polyurethane 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 to form the sole, wherein a melting range of the thermoplastic polyurethane starts below 130° C. when measured by differential scanning calorimetry (DSC) with a heating rate of 20 K/min.

11. The method of claim 10, wherein the sole comprises a midsole.

12. The method of claim 10, wherein the sole comprises an insole.

13. The method of claim 10, wherein the expanded thermoplastic polyurethane beads form the entire sole.

14. The method of claim 10, wherein the sole comprises a density between 8 g/l and 600 g/l.

15. The method of claim 10, wherein the expanded thermoplastic polyurethane beads have a diameter between 0.2 mm and 20 mm.

16. The method of claim 15, wherein the diameter is between 0.5 mm and 15 mm.

17. The method of claim 15, wherein the diameter is between 1 mm and 12 mm.

18. The method of claim 10, wherein fusing the expanded thermoplastic polyurethane beads to one another to form the sole comprises placing the expanded thermoplastic polyurethane beads in a closed mold and exposing the expanded thermoplastic polyurethane beads to a temperature between 100° C. and 140° C.

19. The method of claim 10, wherein the blowing agent comprises between 0.1% and 40% of the total weight of the thermoplastic polyurethane.

Description

EXAMPLE 1

(1) Foam Bead Production

(2) 100 parts of the TPUs stated in Table 1 in the form of pellets each weighing about 2 mg, 250 parts by weight of water, 6.7 parts of tricalcium phosphate, and 20 parts of n-butane were introduced, with stirring, into an autoclave and heated to the temperature stated in Table 2. The contents of the pressure vessel were then discharged through a basal valve and depressurized, while the pressure in the tank was kept constant by introducing, under pressure, nitrogen or the blowing agent used. The foam beads were freed from adherent residues of auxiliaries via washing with nitric acid and water and were air-dried at 50° C.

(3) The impregnation conditions and the resultant bulk densities of the expanded beads are found in Table 2.

(4) TABLE-US-00002 TABLE 2 n-Butane Bulk TPU of [parts Temperature density Table 1 by weight] [° C.] [g/L] A 20 112 300 A 20 114 170 B 20 119 240 B 20 120 190 B 20 122 140 B 20 125 120

EXAMPLE 2

(5) Production of Moldings

(6) The foam beads produced in Example 1 were charged into a preheated mold, with pressure and compaction. The mold was heated by steam at from 1.0 to 4.0 bar, i.e. at temperatures of from 100° C. to 140° C., on alternate sides.

(7) The mold was then depressurized and cooled with water and, respectively, air, and opened, and the mechanically stable molding was removed.