Procedure for obtaining rigid polyisocyanate foam.

Procedure for obtaining materials rigid polyisocyanurate foams by reacting a) isocyanates with b) compounds having groups reactive toward isocyanates, c) blowing agents containing formic acid, d) and e catalyst system) optionally foam stabilizers, flame protection agents and other additives, wherein the catalyst system contains i) at least one compound of the structure: ** (See formula) ** in which R1 is CH3, CH2-CH2-N (CH3) 2 or CH2-CH2OH and R2 is H, CH2-CH2OH or CH2-CH2N (CH3) 2, and at least one trimerization catalyst (ii) selected from ammonium salts, salts of metals alkali or alkaline earth metal salts of a carboxylic acid.