Method and apparatus for producing polyurethane foam using liquid carbon dioxide as a blowing agent

摘要

In a process for adding a metered amount of carbon dioxide into a polyol flow at a pressure just above the equilibrium pressure for the dissolved gas, one or more metered polyol flows (P1, P2 and P3) are combined and a branch pipe (22) feeds part of the flow to a pump (23) which raises the polyol pressure to a suitable level for the addition of the carbon dioxide at a static mixer (24) and maintaining it in a fluid state in the polyol. The part flow then recombines with the main polyol flow and pressure is reduced to a level just above that at which the carbon dioxide vaporises and the polyol flow is mixed with an isocyanate (2). Also claimed are: (i) the production of polyurethane foam using liquid carbon dioxide as the blowing agent; and (ii) the apparatus for the above process, comprising a polyol branch pipe (22) with a pressure increasing pump (23), a carbon dioxide injecting system (25), a static mixer (24) and a by-pass pipe (21) for the main polyol flow, and a pressure holding valve (6) after the recombining point for the branch and main flows, which is followed by a foam component mixer (1) with a pressure relaxation valve (4) at the outlet.