Process for preparing layered foamed polymeric materials

1 . A process for preparing a layered foamed polymeric material with one or more foaming agents, where said method comprises:

providing a foamable polymeric material in a closed reactor and raising the pressure of the one or more foaming agents into the closed reactor up to a maximum of 300 bars;

solubilising said one or more foaming agents in the foamable polymeric material under pressure and at a temperature greater than 20° C.; and

releasing the pressure instantaneously;

wherein said solubilising is carried out with a pressure profile of said one or more foaming agents that is variable over time,

wherein said pressure profile which is variable over time in said solubilising of said one or more foaming agents in said foamable polymeric material generates a non-uniform profile of the concentrations of said one or more foaming agents in said foamable polymer, which upon foaming correspondingly generates a non-uniform morphology and density in said foamed polymeric material and

wherein said pressure profile varies from a minimum pressure equal to atmospheric pressure to a maximum of 300 bars.

2 . The process according to claim 1 , wherein said pressure profile varies over time in a periodic or non-periodic manner.

3 . The process according to claim 2 , wherein said pressure profile varies over time in a periodic manner with a waveform selected from the group consisting of the sinusoidal, triangular, square or sawtooth type, or combinations thereof.

4 . The process according to claim 2 , wherein said pressure profile varies over time in a non-periodic manner following a linear, sectioned, curvilinear, parabolic, exponential, impulsive profile, or combinations thereof.

5 . The process according to claim 1 , wherein said pressure profile comprises at least one step with a pressure profile increasing over time and at least one step with a pressure profile decreasing over time.

6 . The process according to claim 5 , wherein said pressure profile comprises at least one step with a constant pressure profile over time.

7 . The process according to claim 1 , wherein one foaming agent is used.

8 . The process according to claim 1 , wherein a mixture of two or more foaming agents is used.

9 . The process according to claim 8 , wherein the concentration of said foaming agents in said mixture varies over time.

10 . The process according to claim 1 , wherein said one or more foaming agents is selected from the group consisting of an inert gas, carbon dioxide, and a substituted or not substituted aliphatic hydrocarbon (linear, branched or cyclic), having from 3 to 8 carbon atoms.

11 . The process according to claim 10 , wherein said one or more foaming agents is selected from the group consisting of nitrogen, carbon dioxide, n-butane, iso-butane, n-pentane, iso-pentane, 1,1,1,2-tetrafluoroethane (Freon R-134a), 1,1-difluoroethane (Freon R-152a), difluoromethane (Freon R-32), and pentafluoroethane.

12 . The process according to claim 1 , wherein said foamable polymeric material is selected from the group consisting of a thermoplastic polymeric material and a thermosetting polymeric material.

13 . The process according to claim 12 , wherein said thermoplastic polymeric material is selected from the group consisting of a polyolefin, a polyurethane, a polyester and a polyamide.

14 . The process according to claim 12 , wherein said thermosetting polymeric material is selected from the group consisting of a polyurethane, an epoxy resin, a melamine resin, a polyphenol, and a polyimide.