US Patent 11434321 Flame-retardant polyurethane rigid foams

A process for producing rigid PUR/PIR foams via the reaction of a reaction mixture comprising A1 an isocyanate-reactive component, A2 a flame retardant, A3 a blowing agent, A4 a catalyst, and A5 optionally auxiliaries and additives with B an organic polyisocyanate component. Component A1 comprises a diurethane diol A1.1 and a compound A1.2 selected from the group consisting of polyether polyol, polyester polyol, polyether carbonate polyol, and polyether ester polyol. Also disclosed is a rigid PUR/PIR foam, an insulating material, a composite element, and a mixture.