A process can be used for preparing thermally insulating articles containing a thermally insulating polyurethane foam producible in place, a casing surrounding the thermally insulating polyurethane foam, and a foam separator located within the thermally insulating polyurethane foam. The thermally insulating articles producible according to this process are useful. Corresponding cooling systems like fridges, heat storage systems, insulation panels for construction, insulated pipes, mobile transport systems, water boilers, burners, chimneys, instrument panels, roofs of industry hails, engines, or caravans contain the thermally insulating article.

A cavity between inner and outer walls of an open-box-shaped mold is filled with a polyurethane reaction mixture, containing an isocyanate and an emulsion of an isocyanate-reactive composition with three polyols and a blowing agent, which is cured to a polyurethane containing polymer. The inner and outer wall are a fixed distance from one another and each wall comprises a bottom and sides. The mixture is fed through an inlet in the bottom of the outer wall. Before filling the cavity, the mold is turned downwards so that the mixture foams upwards, filling the cavity. The three polyols are polyether polyol obtained by adding an epoxy to carbohydrates or difunctional or higher-functional alcohols; polyether polyol obtained by adding an epoxy to an aromatic amine; and polyester polyether polyol obtained by adding an epoxy to the esterification product of an aromatic dicarboxylic acid derivative and a difunctional or higher-functional alcohol.