Insulating sheets of foamed phenol-aldehyde resin - having on faces hard skins of heat hardenable resin

摘要

Title prod. is obtd. by foaming and aq. mixt of components necessary for formation of the heat-hardenable phenol-aldehyde resin, in contact with mould confining members in which the surface of the mould is coated with a surface active agent in amt sufficient to cause the cells in contact with the mould to collapse and form a hard, non-crumbling skin of heat hardenable resion on the foam. The hard skin makes the sheet abrasion-resistant, gives it support against pressure, and eliminates the need for application of a paper sheet to the surface as in known materials of this kind. The sheets can be used as building materials.