METHOD OF PREPARING CLOSED CELL PHENOL-ALDEHYDE FOAM AND THE CLOSED CELL FOAM THUS PREPARED

摘要

The Abstract of the DisclosureClosed cell phenol-aldehyde foam is prepared bya method which includes a novel frothing and curing technique.An admixture containing a liquid phenol-aldehyde resole resin,a volatile blowing agent, and a surfactant is frothed toproduce a stable froth containing closed cells. The cellwalls are formed of the liquid resole resin and the closedcells are expanded by the blowing agent in gaseous phase.The froth is formed into an uncured shape and the liquidresole resin is cured to the solid state in the presence ofan acid catalyst to produce cured closed cell foam. Theinternal temperature throughout the shape during curing isabove the boiling point of the blowing agent but less than100°C. and is sufficiently low to prevent further expansionof the shape in an amount to rupture the closed cell wallsand thereby form an open cell structure. The liquid resoleresin has a sufficiently low exothermic heat of reaction andthe acid catalyst is present in an amount whereby the internaltemperature of the shape during curing is less than 100°C. andwithin the aforesaid limits. The improved closed cell foamthus prepared is also provided.