| abstract |
A closed cell, rigid polyisocyanurate foam which comprises the reaction product of a polyisocyanate and a polyol in the presence of (a) a hydrogen-containing blowing agent or a mixture of a hydrogen-containing blowing agent and at least one co-blowing agent, and (b) a siloxane oxyalkylene copolymer (i) having a molecular weight below about 7500 and an oxyalkylene portion containing greater than 60 weight percent of oxyethylene units and (ii) being prepared by the reaction of an organohydrogensiloxane with a polyoxyalkylene in an essentially solventless system or in the presence of a high boiling point polar polyol. |