Open-celled rigid polyurethane foam and method for producing the same

Abstract

In order to provide an open-celled rigid polyurethane foam, which realizes a low material cost per unit volume of the foam and excellent surface smoothness because of its unique structure, and a thermal insulation material comprising the foam, an open-celled rigid polyurethane foam which has an open cell content of not less than 99% in a state that a skin layer is left on the foam is produced by foam molding, preferably multiple-stage compression molding, of foaming components containing a polyol component and an isocyanate component with an equivalent ratio of NCO/OH of about 0.55-0.95, and a blowing agent, preferably water, and a thermal insulation material is produced from the foam preferably subjected to a baking treatment by means of far-infrared ray exposure. Further, in order to provide a vacuum insulation material that does not result waste upon production, and provide good appearance and high reliability when used for products such as freezing and refrigerating apparatuses by using the aforementioned open-celled rigid polyurethane foam, a vacuum insulation material is produced by covering the foam as a whole with a container composed of a gas barrier film, reducing internal pressure of the container, and sealing the container to provide the vacuum insulation material.