Attempts at reducing the free formaldehyde content in acid catalyst-cured urea-formaldehyde resins

The experience gained in high-tonnage production of ''Krylamina'' urea-formaldehyde resins has been used to explore the applicability of these resins as thermal insulators for the building industry. The primary goal was to establish the source of emission of free HCHO in the resins cured with an aqueous H3PO4 solution. Most aldehyde was found to collect itself in the liquid left on the resin after the resin had been cured. When added to the H3PO4 catalyst solution, hydrogen peroxide was found to reduce substantially the content of free HCOH in the resin. Various substances were examined as modifiers of the urea-formaldehyde commercial precondensate ''Silekol FO'' to study how they affected the time of gelation, apparent density, cure shrinkage and the surface condition of the cured resin (Table 1). ''Silckol FO'' is the major raw material for ''Krylamina'' foams.