Patent ID: 7435762

Claim:
A rigid polyurethane and/or polyisocyanurate foam having fire resistance comprising: from 1-50% by weight of evenly dispersed expandable graphite particles having an average particle size less than 200 microns, from 99 to 50% by weight of a closed cell polyurethane foam, and a non-halogenated chemical or non-halogenated chemical blend selected from the group consisting of pentane, butane, hexane, heptane, diethyl ether, isopentane, n-pentane and cyclopentane or blends of chemicals from said group as a primary blowing agent such that the foam passes the burning test of Factory Mutual Standard F.M. 4450, Underwriters Laboratories standard UL 1256 and ASTM E84 for class 1 ratings under each test standard.