The present invention relates to a method for producing a rigid foamed
polyisocyanurate material, comprising: (a) an aromatic polyisocyanate; (b) at least one polyether ester
polyol (b1) having an average functional value of 1.7 or more and 2.8 or less and an OH value of 170 KOH / g or more and 270 mg KOH / g or less; and a polyether ester
polyol (b1) having a functional value of 1.7 or more and 2.7 or less and 170 mg KOH / g or more and 280 mg A reaction mixture is formed by mixing (c) a catalyst, (d) a
blowing agent, (e) a
flame retardant, and (f) optionally auxiliary agents and additives, comprising (b1) a polyether ester
polyol (b1) comprising (b1.1) a
dicarboxylic acid composition containing an aromatic
dicarboxylic acid, (b1.2) one or more hydrophobic compounds or derivatives having at least one hydroxyl group and / or carboxyl group, (b1.3) one or more diols having 2 to 6 C atoms, and (b1.4) an average functional value of 2 to 4. The present invention relates to a method for producing a
polyester polyol (b2) obtained by esterification of a polyether polyol produced by
alkoxylation of an initiator or initiator mixture, wherein
polyethylene terephthalate is used in the production of
polyester polyol (b2) in proportion to more than 25% by weight of the total amount of all components used in the production of
polyester polyol (b2), the
mass ratio of polyether ester polyol (b1) to polyester polyol (b2) is 0.3 or more and 3.0 or less, the sum of the
mass fractions of component (b1) and component (b2) is more than 80% by weight of component (b), the
mass fraction of free
monoethylene glycol is 1.4% by weight or less of the sum of components B, C, E and F, and the mixing for forming the reaction mixture is carried out at an
isocyanate index of at least 180. The present invention further relates to a polyol component for producing a
polyisocyanurate rigid foam material according to the present invention and a sandwich element comprising a
polyisocyanurate rigid foam material obtained by the method according to the present invention, in particular a polyisocyanurate rigid foam material.