Method of foaming a milled precursor

1. A method of making a foamed article, comprising:

a) milling, with a computerized numeric control (CNC) machine, a block or sheet of thermoplastic polymer to form a precursor;

b) crosslinking the thermoplastic polymer;

c) heating the precursor to a first temperature to soften the thermoplastic polymer;

d) infusing the thermoplastic polymer with at least one inert gas at a first pressure that is sufficient to cause the at least one inert gas to permeate into the softened thermoplastic polymer; and

e) at a time when the thermoplastic polymer is heated to a temperature at which the thermoplastic polymer is softened, reducing pressure to a second pressure below the first pressure to at least partially foam the precursor into a foamed article,

wherein the foamed article is substantially a same shape as the precursor.

2. The method according to claim 1 , wherein the foamed article is a partially foamed article, and wherein the method further comprises:

reheating the partially foamed article, under pressure, to a temperature at which the thermoplastic polymer softens; and

reducing pressure to further foam the thermoplastic polymer.

3. The method according to claim 2 , wherein the step of reducing pressure to further foam the thermoplastic polymer is carried out in a mold or a partial mold.

4. The method according to claim 1 , wherein after the infusing and prior to the at least partial foaming, transferring the precursor from a first location to a second location.

5. The method according to claim 4 , wherein the second location is a mold.

6. The method according to claim 4 , wherein the second location is a remote site from the first location.

7. The method according to claim 1 , further comprising:

f) heating the at least partially foamed thermoplastic polymer to a temperature at which the thermoplastic polymer is soften and again infusing that soften thermoplastic polymer with at least one inert gas at a pressure that is sufficient to cause the at least one inert gas to permeate into that softened thermoplastic polymer; and

g) reducing pressure to further foam the softened thermoplastic polymer.

8. The method according to claim 1 , wherein the precursor and foamed article are in a shape of a footwear midsole or a part of a footwear midsole.

9. A method of making a foamed article, comprising:

a) milling, with a computerized numeric control (CNC) machine, a block of a first thermoplastic polymer to form a precursor;

b) crosslinking the first thermoplastic polymer;

c) heating the precursor to a first temperature to soften the precursor;

d) infusing the precursor with a first inert gas under a first pressure;

e) cooling the precursor to a second temperature below the first temperature;

f) reducing pressure to a second pressure lower than the first pressure; and

g) heating the precursor to a third temperature at a third pressure to at least partially foam the precursor and form a foamed article.

10. The method according to claim 9 , further comprising decreasing pressure from the third pressure to a fourth pressure lower than the third pressure to induce further foaming.

11. The method according to claim 9 , further comprising:

moving the precursor from a first location to a second location after pressure is reduced to the second pressure and before the precursor is heated to the third temperature.

12. The method according to claim 11 , wherein the second location is a mold or a partial mold.

13. The method according to claim 11 , wherein the second location is a partial mold, and wherein the partial mold or a portion of the partial mold is adhesively attached to or physically attached to the foamed article.

14. A method of making a foamed article selected from the group consisting of: a footwear midsole, a part of a footwear midsole, a footwear upper, a footwear collar, a footwear tongue, and a footwear insole, comprising:

a) milling with a computerized numeric control (CNC) machine, a block of a first thermoplastic polymer to form a precursor in a shape selected from the group consisting of: a footwear midsole, a part of a footwear midsole, a footwear upper, a footwear collar, a footwear tongue, and a footwear insole;

b) crosslinking the first thermoplastic polymer;

c) heating the precursor to a first temperature to soften the precursor;

d) infusing the precursor with a first inert gas under a first pressure;

e) cooling the precursor to a second temperature below the first temperature;

f) reducing pressure to a second pressure lower than the first pressure;

g) heating the precursor to a third temperature at a third pressure; and

h) decreasing pressure to a fourth pressure lower than the third pressure to induce foaming and form the foamed article, wherein the foamed article is a member selected from the group consisting of: a footwear midsole, a part of a footwear midsole, a footwear upper, a footwear collar, a footwear tongue, and a footwear insole, and wherein a volume of the precursor is at least 20% and up to 80% of a volume of the foamed article.

15. The method according to claim 14 , further comprising:

moving the precursor from a first location to a second location after pressure is reduced to the second pressure and before the precursor is heated to the third temperature.

16. The method according to claim 15 , wherein the second location is a mold or a partial mold.

17. The method according to claim 15 , wherein the second location is a partial mold, and wherein the partial mold or a portion of the partial mold is adhesively attached to or physically attached to the foamed article.

18. The method according to claim 14 , wherein the foamed article is a footwear midsole.