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

1. A polyurethane foam having a density of 90 to 180 kg/m 3 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.

2. The foam of claim 1 in which b)(2) includes from 5 to 15% amino groups, based on the amount of b)(2).

3. The foam of claim 1 in which b)(2) has an equivalent weight of from 100 to 160 g/mol.

4. A process for the production of the polyurethane foam of claim 1 comprising reacting a) with b) in the presence of c), d) and optionally, e) in amounts such that the ratio of NCO groups to isocyanate-reactive groups is in the range from 0.9:1 to 1:0.9 and the ratio of the number of urea groups formed to the number of urethane groups formed is in the range from 1:1 to 2.5:1.

5. The process of claim 4 in which b)(2) includes from 5 to 15% amino groups, based on the amount of b)(2).

6. The process of claim 4 in which b)(2) has an equivalent weight of from 100 to 160 g/mol.

7. A composite element comprising the polyurethane foam of claim 1 .

8. The composite element of claim 7 further comprising a backing and a covering skin selected from the group consisting of a thermoplastic, elastomer, thermoset, wood, leather and metal.

9. The composite element of claim 8 in which the covering skin is a fiber-reinforced thermoplastic.

10. A lining for a motor vehicle interior comprising the composite of claim 8 .