Process for preparing a rigid polyurethane foam and laminate articles therewith

A process for preparing a rigid polyurethane foam by contacting under reaction conditions a urethane-modified polyisocyanate with a polyahl in the presence:of a blowing agent characterized in that:

• a) the urethane-modified polyisocyanate has an isocyanate content of from about 10 to about 29 weight percent and is the reaction product of a polymethylene polyphenylisocyanate having an average isocyanate functionality of from about 2.5 to about 3.5 with a polyoxyalkylene polyol having a molecular weight of at least 2000 and an oxyethylene content of at least 50 weight percent;
• b) the blowing agent comprises from about 1 to about 10 parts of water per 100 parts by weight of polyahl and is free of any perhalogenated hydrocarbon, with the exception of perfluoroalkanes,
• wherein the urethane-modified polyisocyanate is present in an amount to provide from about 0.7 to about 2 isocyanate groups per isocyanate-reactive hydrogen atom present from the polyahl and water.