Patent ID: 7714030

Claim:
A method of forming a rigid polyurethane structural reinforcement, vibration dampening or sound dampening foam attached to an open cavity of a vehicular part or assembly, comprising mixing a polyisocyanate component with a polyol component in the presence of a blowing agent and at least one catalyst for the reaction of a polyol with a polyisocyanate, dispensing the resulting mixture into the cavity of the vehicular part or assembly and subjecting the mixture to conditions sufficient to cause it to cure to form a foam having a bulk density of 1.5 to 40 pounds per cubic foot (24-640 kg/m 3 ) that is adherent to the substrate, wherein (a) the polyisocyanate component contains at least one prepolymer containing oxazolidone groups and free isocyanate groups, (b) the polyol component contains isocyanate-reactive materials that have an average functionality of at least about 2.0 and include at least one polyol, and (c) the ratio of isocyanate groups in the polyisocyanate component to the number of isocyanate-reactive groups in the polyol component is from about 0.7:1 to about 1.5:1.