Abstract: A continuous process for the production of flame-resistant foamed plastics material by condensation of aqueous aminoplast precondensates with diisocyanates or polyisocyanates, wherein, in a first mixing stage, the isocyanate is mixed with 4 to 14% by weight of catalyst, the catalyst being an organic amine and/or an organic metal compound, at temperatures of 40.degree. to 130.degree. C., with a residence time of 1 to 8 seconds, and directly thereafter, in a second mixing stage, the aminoplast precondensate and, simultaneously but separately from the aminoplast, an acid curing catalyst are introduced, after which the foamable mixture thereby produced is discharged continuously.

Abstract: Production of foamed plastics with improved combustion characteristics by condensing aqueous solutions of aminoplast precondensates with at least bifunctional organic isocyanate whereby an acid curing catalyst and an accelerator for polyurethane formation is used. For performing the condensation, the aqueous solution of the precondensate is added to the mixture of isocyanate and the accelerator at the same time as but separately from the acid curing catalyst.

Abstract: Foamed plastics with improved combustion characteristics and good mechanical strength are obtained by condensation of aminoplast precondensates with organic isocyanates in the presence of an acid curing catalyst and an accelerator for polyurethane formation, whereby the precondensate used as starting material is prepared by reacting formaldehyde with urea and/or melamine in a molar ratio of 1.80 to 4.5:1 at pH values of 4 to 9.5, adjusting then the pH to 7.0 to 8.0 and adding urea to obtain a molar ratio offormaldehyde to the total amount of aminoplast forming compound of 1.0-2.1:1.