Semi-rigid polyurethane foams and processes for their production and use

A polyurethane foam having a density of 90 to 180 kg/m3 and a compressive strength of from 20 to 95 kPa comprising the reaction product of

• a) at least one organic polyisocyanate and/or modified organic polyisocyanate, wherein the least one organic polyisocyanate and/or modified organic polyisocyanate is based on diphenylmethane diisocyanate and/or polyphenyl polymethylene polyisocyanate,
• and
• b) an isocyanate-reactive component comprising:
• (1) 84 to 99.5 weight %, based on total weight of b), of at least one polyether polyol derived from ethylene oxide and/or propylene oxide having a weight-average equivalent weight of from 1000 to 3000 g/mol and an average functionality of from 2 to 8,
• (2) 0.5 to 6 weight %, based on total weight of b), of at least one polyether polyol derived from ethylene oxide and/or propylene oxide with diaminotoluene as starter having a weight-average equivalent weight of 90-190 g/mol wherein the toluenediamine is 2,3-diaminotoluene and/or 3,4-diaminotoluene, wherein the 2,3-diaminotoluene and/or 3,4-diaminotoluene contains up to 20 weight % of 2,4- and/or 2,6-diaminotoluene
• and
• (3) 0 to 10 weight %, based on total weight of b), of chain-extending agent and/or crosslinker,
• formed in the presence of
• c) a catalyst,
• d) from 1 to 5 weight %, based on total weight of b) to e), of water, and
• e) optionally, auxiliaries and/or addition agents,
• at an NCO group to isocyanate-reactive group ratio of from 0.9:1 to 1:0.9 in which the ratio of the number of urea groups formed to the number of urethane groups formed is from 1:1 to 2.5:1.