Method for producing three dimensional foam articles

A process for making a three dimensional foam article of non-uniform shape comprising the steps of:

• (a) providing a pre-form comprising a polymer in a pressure vessel;
• (b) subjecting the pre-form to at least one inert gas at a pressure higher than atmospheric in order to drive gas into the pre-form;
• (c) raising the temperature of the pre-form to or above its softening point, wherein steps (b) and (c) can take place in any order or simultaneously;
• (d) reducing the pressure to a pressure higher than atmospheric pressure but lower than the pressure of step (b) and then cooling the pre-form to below its softening point to result in a partially expanded article;
• (e) transferring said article to a second vessel and heating it to a temperature above its softening point under a pressure of inert gas or air;
• and
• (f) reducing the pressure whilst maintaining the temperature at or above the softening point of the polymer, in order to expand the partially expanded article to form a foamed article;
• wherein the cross-section of the polymer pre-form in at least one dimension is non-uniform.