Patent ID: 6809124
Filing Date: 2004-10-26
Classification: B29C,C08G,C08J

Abstract:
In a process for the production of polyurethane block foam, comprising 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, the improvement wherein 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.