Method for the preparation of polyether polyols

1. A method for the preparation of polyether polyols ( 1 ) with a hydroxyl value of 3 mg KOH/g to 150 mg KOH/g, comprising

(i) preparing a component A) by

(i-1) forming a crude alkoxylate with an equivalent molar mass of 53Da to 350 Da by reacting a first H-functional starter compound A 1 . 1 ) with one or more alkylene oxides A 1 . 2 ) in the presence of a basic catalyst, and then

(i-2) neutralizing said crude alkoxylate with sulfuric acid, wherein the neutralisation of the alkaline, polymerisation-active centres of said crude alkoxylate is carried out by addition of sulfuric acid such that for from 66 mol % to 100 mol % of the acid used, only the first dissociation step of sulfuric acid is effective for neutralisation of the amount of catalyst present in the crude alkoxylate, and the separation of the salts formed being dispensed with,

and

(ii) reacting said component A) with one or more alkylene oxides B 1 ) in the presence of a DMC catalyst B 2 ).

2. The method according to claim 1 , wherein after step (i-2) in step (i-3) the removal of reaction water and traces of water introduced with the acid takes place at an absolute pressure of 1 to 500 mbar and at temperatures of 20 to 200° C.

3. The method according to claim 1 , wherein said basic catalyst comprises at least one compound selected from the group consisting of alkali metal hydroxides, alkaline-earth metal hydroxides, alkali metal hydrides, alkaline-earth metal hydrides, alkali metal carboxylates and alkaline-earth metal carboxylates.

4. The method according to claim 1 , wherein said basic catalyst comprises an alkali metal hydroxide.

5. The method according to claim 1 , wherein said basic catalyst is selected from the group consisting of sodium hydroxide, potassium hydroxide, caesium hydroxide and mixtures thereof.

6. The method according to claim 1 , wherein the concentration of basic catalyst is 40 ppm to 5,000 ppm, relative to the resulting amount of crude alkoxylate product.

7. The method according to claim 1 , characterised in that at least one amine is used as basic catalyst.

8. The method according to claim 1 , wherein in step (ii) a second H-functional starter compound and DMC catalyst B 2 ) are initially introduced into the reactor system, and component A) is supplied continuously together with one or more alkylene oxides B 1 ).

9. The method according to claim 8 , wherein in step (ii) said second H-functional starter compound comprises a polyether polyol end product ( 1 ) according to the invention, which has been prepared separately beforehand.

10. The method according to claim 8 , wherein in step (ii) said second H-functional starter compound comprises component A).

11. The method according to claim 1 , wherein in step (ii) the entire amount of component A) and DMC catalyst B 2 ) are initially introduced and one or more third H-functional starter compounds are supplied continuously together with one or more alkylene oxides B 1 ).

12. The method according to claim 1 , wherein in step (ii) a second H-functional starter compound and a DMC catalyst B 2 ) are initially introduced into the reactor system, and component A) is supplied jointly continuously with one or more alkylene oxides B 1 ) and DMC catalyst B 2 ), and the resultant polyether polyol ( 1 ) is removed continuously from the reactor system as reaction product.

13. The method according to claim 12 , wherein in step (ii) said second H-functional starter compound comprises polyether polyol end product ( 1 ) according to the invention, which has been prepared separately beforehand.

14. The method according to claim 12 wherein in step (ii) said second H-functional starter compound comprises component A).

15. The method according to claim 1 , wherein said one or more alkylene oxides A 1 . 2 ) to be metered in step (i-1) comprise at least 10% by weight ethylene oxide, based on 100% by weight of said alkylene oxides.

16. The method according to claim 1 , wherein component A) is split into two portions, and in step (ii) a second H-functional starter compound and DMC catalyst B 2 ) are initially introduced into the reactor system, with said second H-functional starter compound comprising a first portion of component A) and the second portion of component A) is supplied continuously together with one or more alkylene oxides B 1 ).

17. The method according to claim 1 , wherein component A) is split into two portions, in step (ii) a second H-functional starter compound and DMC catalyst B 2 ) are initially introduced into the reactor system, with said second H-functional starter compound comprising a first portion of component A), and the second portion of component A) is supplied jointly continuously with one or more alkylene oxides B 1 ) and DMC catalyst B 2 ), and the resultant polyether polyol ( 1 ) is removed continuously from the reactor system as reaction product.

18. Polyether polyols produced by the process of claim 1 .

19. A polyurethane comprising the reaction product of one or more polyether polyols according to claim 18 with at least one polyisocyanate component.