COMPOSITE ELEMENTS WITH IMPROVED DIMENSIONAL STABILITY

1 .- 12 . (canceled)

13 . A polyurethane/polyisocyanurate foam, obtained from the reaction of

A) an isocyanate-reactive composition comprising

A1) from 0 to 15 wt. % of at least one polyester polyol having a hydroxyl number in the range of from 300 mg KOH/g to 1000 mg KOH/g, determined in accordance with DIN 53240,

A2) from 1 to 15 wt. % of at least one polyether polyol having a hydroxyl number in the range of from 300 mg KOH/g to 600 mg KOH/g, determined in accordance with DIN 53240,

and

A3) from 50 to 70 wt. % of at least one polyester polyol having a hydroxyl number in the range of from 80 mg KOH/g to 290 mg KOH/g, determined in accordance with DIN 53240,

wherein the data in wt. % are based in each case on all the components of the isocyanate-reactive composition A);

with

B) a polyisocyanate component,

wherein the equivalent ratio of NCO groups to the sum of the hydrogen atoms reactive towards NCO groups is from ≧150:100 to ≦500:100,

wherein the polyether polyol A2) is a polyether polyol A2) started with an aromatic amine.

14 . The polyurethane/polyisocyanurate foam according to claim 13 , wherein the equivalent ratio of NCO groups to the sum of the hydrogen atoms reactive towards NCO groups is from ≧150:100 to ≦400:100.

15 . The polyurethane/polyisocyanurate foam according to claim 13 , wherein the isocyanate-reactive composition comprises from 1 to 10 wt. % of at least one polyester polyol A1), from 1 to 10 wt. % of at least one polyether polyol A2) and from 50 to 70 wt. % of at least one polyester polyol A3).

16 . The polyurethane/polyisocyanurate foam according to claim 13 , wherein polyisocyanate component B) comprises a mixture of diphenylmethane 4,4′-diisocyanate with isomers and higher functional homologues.

17 . The polyurethane/polyisocyanurate foam according to claim 13 , wherein the isocyanate-reactive composition comprises trimerisation catalysts D) selected from the group consisting of ammonium, alkali, and alkaline earth metal salts of carboxylic acids.

18 . The polyurethane/polyisocyanurate foam according to claim 13 , wherein the aromatic amine is selected from the group consisting of toluylenediamine, diaminodiphenylmethane and polymethylene-polyphenylene-polyamine.

19 . A method for producing a composite element comprising utilizing the polyurethane/polyisocyanurate foam according to claim 13 .

20 . A composite element comprising at least one covering layer and at least one layer that comprises a polyurethane/polyisocyanurate foam according to claim 13 .

21 . The composite element according to claim 20 , wherein the covering layer is a metal layer.

22 . A method for producing a composite element comprising applying, in at least one step a reaction mixture comprising components A) and B) according to claim 13 , to a covering layer.

23 . The method according to claim 22 , wherein the covering layer is a metal layer.

24 . The method according to claim 22 , wherein the method is configured as a twin conveyor belt method.