Controlled cooling of porous materials

A method for cooling polyurethane foam which comprises:

• passing first gases through hot polyurethane foam which contains volatiles generated by formation of the foam in a first zone at a predetermined flow rate to cool the foam and to remove at least a portion of such volatiles including at least one of toluene diisocyanate, butylated hydroxy toluene, chlorofluorocarbons, or other auxiliary blowing agents therefrom in a first gas mixture which exits the foam at a predetermined temperature;
• controlling the flow rate of the first gases through the foam to provide a controlled uniform cooling rate which produces improved physical properties of the foam;
• mixing the first gas mixture with second gases having a temperature which is lower than that of the first gas mixture, thus forming a second gas mixture having a temperature which is sufficiently low to condense or sublime a portion of one or more of the volatiles;
• passing the second gas mixture through the foam in a second zone to filter the condensed or sublimed volatiles thereon and to further cool the foam;
• withdrawing a third gas mixture which exits the foam from the second zone;
• recirculating a first portion of the third gas mixture as the second gases for mixing with the first gas mixture;
• and
• withdrawing a second portion of the third gas mixture for recovery of the volatiles which do not condense or sublime at the temperature of the third gas mixture.