METHOD FOR PRODUCING FLAME-PROTECTED POLYURETHANE FOAMS HAVING LOW BULK DENSITIES

1 - 14 . (canceled)

15 . Method for producing flame-retardant polyurethane foams comprising the following steps:

Step (1) producing a flexible polyurethane foam obtainable by reacting Component A:

A1 100 parts by weight of compounds containing isocyanate-reactive hydrogen atoms and having a hydroxyl value in accordance with DIN 53240 from 3 mg KOH/g to 140 mg KOH/g,

A2.1 0.5 to 25 parts by weight, per 100 parts by weight of A1, of water,

A2.2 0 to 25 parts by weight, per 100 parts by weight of A1, of physical blowing agent,

A3 0 to 10 parts by weight, per 100 parts by weight of A1, of compounds containing optionally isocyanate-reactive hydrogen atoms and having a hydroxyl value from 140 mg KOH/g to 900 mg KOH/g,

A4 0.05 to 10 parts by weight, per 100 parts by weight of A1, of auxiliary agents and additives,

and

Component B:

B di- or polyisocyanates,

wherein production of said flexible polyurethane foam takes place with an isocyanate index from 75 to 120, and

wherein the indicated parts by weight of components A2 to A4 relate to 100 parts by weight of component A1;

Step (2) impregnating the flexible polyurethane foam produced in step (1) with aqueous sodium and/or potassium silicate solution,

Step (3) periodically compacting and/or rolling the impregnated polyurethane foam from step (2), then

Step (4) drying the polyurethane foam obtainable in accordance with step (3).

16 . The method according to claim 15 , wherein the auxiliary agents and additives are selected from the group consisting of catalysts, surface-active agents, pigments and flame retardants.

17 . The method according to claim 15 , wherein component A1 contains:

A1.1 at least one polyether polyol having a functionality from 2 to 8, an oxyethylene content of >60 wt. %, primary OH groups and a hydroxyl value in accordance with DIN 53240 from ≧10 mg KOH/g to ≦112 mg KOH/g, and

A1.2.1 at least one polyether polyol having a functionality from 2 to 8, an oxyethylene content from 0 to 30 wt. %, less than 50% primary OH groups and a hydroxyl value in accordance with DIN 53240 from ≧42 mg KOH/g to ≦56 mg KOH/g, and/or

A1.2.2 at least one polyether polyol having a functionality from 2 to 8, an oxyethylene content from 0 to 30 wt. %, more than 50% primary OH groups and a hydroxyl value in accordance with DIN 53240 from ≧28 mg KOH/g to ≦35 mg KOH/g,

the indicated parts by weight of components A1.1, A1.2.1 and A1.2.2 adding to 100.

18 . The method according to claim 15 , wherein component A1 contains 100 parts by weight of a polyether polyol having a hydroxyl value in accordance with DIN 53240 from 3 mg KOH/g to 140 mg KOH/g, a functionality from 2 to 8 and an oxyethylene content from 0 to 20 wt. %.

19 . The method according to claim 17 , wherein component A1 contains:

A1.1 60 to 90 parts by weight of a polyether polyol having a functionality from 2 to 8, an oxyethylene content of >60 wt. %, more than 50% primary OH groups and a hydroxyl value in accordance with DIN 53240 from ≧10 mg KOH/g to ≦112 mg KOH/g, and

A1.2.1 10 to 40 parts by weight of a polyether polyol having a functionality from 2 to 8, an oxyethylene content from 0 to 30 wt. %, less than 50% primary OH groups and a hydroxyl value in accordance with DIN 53240 from ≧42 mg KOH/g to ≦56 mg KOH/g, and/or

A1.2.2 10 to 40 parts by weight of a polyether polyol having a functionality from 2 to 8, an oxyethylene content from 0 to 30 wt. %, more than 50% primary OH groups and a hydroxyl value in accordance with DIN 53240 from ≧28 mg KOH/g to ≦35 mg KOH/g,

the indicated parts by weight of components A1.1, A1.2.1 and A1.2.2 adding to 100.

20 . The method according to claim 15 , wherein in step (1) the flexible polyurethane foam has a density of less than 25 kg/m 3 .

21 . The method according to claim 15 , wherein in step (1) the flexible polyurethane foam has a density of less than 15 kg/m 3 .

22 . The method according to claim 15 , wherein after step (4) the polyurethane foam has a density of less than 60 kg/m 3 .

23 . The method according to claim 15 , wherein after step (4) the polyurethane foam has a density of ≦45 kg/m 3 and ≧38 kg/m 3 .

24 . The method according to claim 15 , wherein after step (4) the polyurethane foam has a density of ≦30 kg/m 3 and ≧23 kg/m 3 .

25 . A polyurethane foam obtainable by the method according to claim 15 .

26 . The polyurethane foam according to claim 25 , having a density of less than 60 kg/m 3 .

27 . The polyurethane foam according to claim 25 , having a density of ≦45 kg/m 3 and ≧38 kg/m 3 .

28 . The polyurethane foam according to claim 25 , having a density of ≦30 kg/m 3 and ≧23 kg/m 3 .

29 . Use of the polyurethane foams according to claim 25 in the automotive, construction and/or furniture industry.