| 摘要 |
Closed cell phenol-aldehyde foam is prepared by a method which includes a novel frothing and curing technique. An admixture containing a liquid phenolaldehyde resole resin, a volatile blowing agent, and a surfactant is frothed to produce a stable froth containing closed cells. The cell walls are formed of the liquid resole resin and the closed cells are expanded by the blowing agent in gaseous phase. The froth is formed into an uncured shape and the liquid resole resin is cured to the solid state in the presence of an acid catalyst to produce cured closed cell foam. The internal temperature throughout the shape during curing is above the boiling point of the blowing agent but less than 212 DEG F., and is sufficiently low to prevent further expansion of the shape in an amount to rupture the closed cell walls and thereby form an open cell structure. The liquid resole resin has a sufficiently low exothermic heat of reaction and the acid catalyst is present in an amount whereby the internal temperature of the shape during curing is less than 212 DEG F. and within the aforesaid limits. The improved closed cell foam thus prepared is also provided. |
