Method of making cured aminoplast foam

Claim 1

In a method of making a cured foamed aminoformaldehyde product by (a) dispersing a curing catalyst and a blowing agent in a liquid aminoformaldehyde precondensate to obtain a liquid foamable composition, and (b) heating the composition to a temperature such as to cause the flowing agent to form a foam and the aminoformaldehyde precondensate to cure, the improvement which consists in (1) employing as the aminoformaldehyde precondensate one that has a water content less than 20% by weight and a viscosity in the range of about 400 to about 1300 poise at 25° C., and is obtained from a reaction mixture which consists essentially of urea, a source of formaldehyde selected from paraformaldehyde and hexamine, and a reaction modifier to maintain the reaction mixture in the liquid phase, said modifier being selected from ethylene urea, a melamine-formaldehyde precondensate, melamine, diethylene glycol, polyvinyl alcohol, a water-soluble carbohydrate, and dicyandiamide, and (2) formulating the foamable composition so that, at the temperature at which foaming begins, its viscosity is in the range 100-1000 poise.