Single-phase solution molding

Patent metadata

Field	Value
Publication number	US-2018345544-A1
Application number	US-201815993022-A
Country	US
Kind code	A1
Filing date	May 30, 2018
Priority date	May 31, 2017
Publication date	Dec 6, 2018
Grant date	—

Abstract

Aspects hereof provide methods for molding a single-phase solution comprised of a polymer composition and a gas. The polymer composition and the gas are maintained under pressure during the molding operation to prevent a cellular structure from being formed by the dissolved gas in the polymer composition coming out of solution. The mold cavity in which the single-phase solution is introduced for molding purposes is pressurized to a mold pressure that is sufficient to maintain the single-phase solution as a single-phase solution as the mold cavity is filled. Subsequent to filling the mold cavity with the single-phase solution under pressure, the resulting article may solidify entrapping the compressed gas, or the article may be exposed to a reduction in pressure causing the entrapped gas to form a cellular structure.

First claim

The invention claimed is:

1 . A method of molding a single-phase solution, the method comprising:
forming the single-phase solution, wherein the single-phase solution is comprised of a polymer composition and a gas; pressurizing a mold cavity of a mold above atmospheric pressure to a mold pressure, wherein the mold pressure is at least a pressure to maintain the single-phase solution as a single phase; injecting the single-phase solution into the mold cavity; and maintaining at least the mold pressure in the mold cavity during the injecting of the single-phase solution.

2 . The method of claim 1 , wherein forming the single-phase solution comprises dissolving the gas with the polymer composition while the polymer composition is at least at a glass transition temperature.

3 . The method claim 1 , wherein forming the single-phase solution comprises dissolving the gas with the polymer composition while the polymer composition is below a glass transition temperature.

4 . The method of claim 1 , wherein forming the single-phase solution comprises dissolving the gas with the polymer composition while the gas is in a super-critical fluid state.

5 . The method of claim 1 , wherein forming the single-phase solution comprises dissolving the gas with the polymer composition while the gas is above atmospheric pressure.

6 . The method of claim 1 , wherein the polymer composition is comprised of a polymer selected from one of polyurethane and ethylene-vinyl acetate.

7 . The method of claim 1 , wherein the gas is selected from carbon dioxide (CO2) and nitrogen (N2).

8 . The method of claim 1 , wherein the single-phase solution does not comprise a chemical-reaction foaming agent.

9 . The method of claim 1 , wherein the single-phase solution comprises a cross-linking agent.

10 . The method of claim 1 , further comprising heating the mold above an ambient temperature prior to injecting the single-phase solution.

11 . The method of claim 1 , wherein the mold comprises a pressure regulator that maintains at least the mold pressure as the single-phase solution is injected into the mold cavity and wherein the mold cavity remains a constant volume.

12 . The method of claim 1 , further comprising filling the mold cavity at least 80% by mold-cavity volume with the single-phase solution prior to the single-phase solution converting to a two-phase polymer and gas mixture.

13 . The method of claim 12 , wherein the single-phase solution is a homogenous mixture and the two-phase polymer and gas mixture is a heterogeneous mixture.

14 . The method of claim 1 , further comprising cooling the single-phase solution below a glass transition temperature of the polymer and gas solution to form a single-phase solid article.

15 . The method of claim 14 , further comprising heating the single-phase solid article to form a two-phase mixture.

16 . The method of claim 15 , wherein heating the single-phase solid article to form a two-phase mixture is performed in a second mold.

17 . The method of claim 16 , wherein the second mold is pressurized above atmospheric pressure to a second mold pressure prior to the single-phase solid article being formed into the two-phase mixture.

18 . The method of claim 1 , where cross-linking of the polymer composition occurs prior to a foaming of the polymer composition.

19 . A method of molding a single-phase solution, the method comprising:
mixing a polymer composition above a glass transition temperature of the polymer composition with a gas above atmospheric pressure to form the single-phase solution; pressurizing a mold cavity of a mold above atmospheric pressure to a mold pressure, wherein the mold pressure is at least a pressure to maintain the single-phase solution as a homogeneous mixture; while maintaining the mold cavity at least at the mold pressure, filling the mold cavity with the single-phase solution; while maintaining the mold cavity at least at the mold pressure, cross-linking the polymer composition in the mold cavity; and depressurizing the mold cavity to a depressurization pressure that converts the single-phase solution to a heterogeneous mixture comprised of the polymer composition and the gas.

20 . A method of molding a single-phase polymer and gas solution, the method comprising:
mixing a polymer composition above a glass transition temperature of the polymer composition with a gas above atmospheric pressure to form the single-phase solution; pressurizing a first mold cavity of a mold above atmospheric pressure to a mold pressure, wherein the mold pressure is at least a pressure to maintain the single-phase solution as a homogeneous solution; while maintaining the first mold cavity at least at the mold pressure, injecting the single-phase solution into the first mold cavity; cooling the single-phase solution below the glass transition temperature to form a single-phase solid article in the first mold cavity; and depressurizing the first mold cavity below the molding pressure.

21 . The method of claim 20 further comprising:
transferring the single-phase solid article to a second mold having a second mold cavity; and
heating the single-phase solid article within the second mold cavity to convert the single-phase solid article to a foamed article.

22 . The method of claim 21 wherein the second mold cavity has a larger volume than the first mold cavity.

Assignees

• Nike Inc

Inventors

• Darland Jeffrey E
• Mace Ryan Alvin

Classifications

• B29C44/3453

  Feeding the blowing agent to solid plastic material · CPC title

• B29C44/08

  using several expanding {or moulding} steps · CPC title

• B29K2105/24

  crosslinked or vulcanised · CPC title

• B29K2075/00

  Use of {PU, i.e.} polyureas or polyurethanes {or derivatives thereof}, as moulding material · CPC title

• B29C45/0001

  characterised by the choice of material · CPC title