activity and should be used in a larger amount requiring a longer cream time and giving a rapid foaming profile the resulting foam had a broad density distribution and poor moldability in the fire retardance test the resulting foam had a relatively high oxygen index but smoke generation is significant with unsatisfactory balance of the fire retardance the surface of the obtained foam has a high friability and a high thermal conductivity flexible isocyanurate foams were prepared with formulations of the polyol and the polyisocyanate shown in table 2 isocyanate index 105 by using respectively catalysts a b c and e produced in production examples 1 3 and 5 and a blowing agent and a foam stabilizer as shown in table 2 the products were tested and evaluated for the reactivity cream time gel time and rise time of the flexible isocyanurate foam the delaying effect elongation in seconds of cream time of the respective catalyst in comparison with catalyst l33 as the reference and the properties density and air permeability of the foam products table 2 shows the evaluation results table 2 shows that the quaternary ammonium salt catalysts of the present invention enable delaying of the initial reaction cream time the catalysts corrode only little the metallic materials and give a foam product having a low density and a high air permeability further the catalyst exudes less odor thereby improving.