Dimensionally stable closed cell rigid polyisocyanate based foam

Abstract

There is now provided a closed cell rigid polyisocyanate based foam blowing with a C.sub.1 -C.sub.4 hydrofluorocarbon and water as blowing agents, which possesses a uniform density gradient varying by not more than 10 percent. There is also now provided a froth foaming mixture having good flow by employing a hydroxy terminated polyol which is pH neutral and a tertiary amine ether blow catalyst in an amount of 0.5 weight percent or more, using water and a C.sub.1 -C.sub.4 hydrofluorocarbon having a boiling point of 300 K or less as co-blowing agents. There is also provided a polyol composition having an average OH number of less than 400 and an average functionality of greater than 4, which when reacted with the isocyanate in the presence of a C.sub.1 -C.sub.4 hydrofluorocarbon, yields a rigid closed cell polyisocyanate based dimensionally stable foam. The formulation according to an especially preferred embodiment of the invention simultaneously satisfies the following requirements: 1) a formulated polyol composition having a viscosity of 550 cP or less; 2) the isocyanate stream and the formulated polyol stream dispensable at a 0.9:1 to 1.3:1 weight ratio, respectively; 3) frothing when dispensed from a static mixer; 4) produces a frothing foaming mixture having excellent flow characteristics as demonstrated by a substantially uniform density gradient; 5) and produces a dimensionally stable closed cell foam having a low overall density of 2.5 pcf or less.