Method for the production of block foam

Abstract

The present invention is directed to an improved process for producing block foam from polyurethane forming component wherein dissolved carbon dioxide is used as a blowing agent. The process broadly comprises a) suddenly expanding a polyurethane reactive mixture containing carbon dioxide from a pressure above the equilibrium solution pressure of the carbon dioxide to normal pressure, the liquid polyurethane reactive mixture foams with the release of dissolved carbon dioxide, b) applying the foamed mixture to a substrate and c) curing the foamed mixture to form block foam>In the improved process, i) the carbon dioxide is initially completely dissolved in the reactive mixture, or in at least one of the components, either polyol and isocyanate, at a first pressure substantially above the equilibrium solution pressure, ii) the pressure is then reduced to a value close to the equilibrium solution pressure, falling in the meantime below the equilibrium solution pressure with the release of small amounts of carbon dioxide to form a bubble microdispersion, iii) the components are mixed, if necessary, and iv) the pressure is suddenly reduced to normal pressure before the released carbon dioxide is completely redissolved. The invention is also directed to a pressure-maintaining device useful in producing polyurethane foams.

Dependencies are inferred from the claim text.