Organically modified siloxanes and their use for producing preparations for water-repellent impregnations for mineral building materials

1. An organomodified siloxane compound of the general formula (I)

where

the radicals R 1 are identical or different radicals selected from the group consisting of linear or branched, saturated or monounsaturated or polyunsaturated alkyl, aryl, alkylaryl or arylalkyl radicals having from 1 to 20 carbon atoms,

the radicals R 2 are identical or different alkylene radicals which have from 1 to 20 carbon atoms,

R 3 is an oxyalkylene radical of the formula (II),

 where

R 3a , R 6a , R 6b are each, independently of one another, hydrogen, preferably methyl and/or ethyl or can each be a branched or unbranched, unsubstituted or heteroatom-substituent-bearing, saturated or unsaturated alkyl or aryl radical and

k is from 2 to 11,

a, b are each, independently of one another, a number in the range from 1 to 4 and

n a , n b are each, independently of one another, a number in the range from 0 to 50, where 1<n a +n b ≦50,

with the proviso that a random or blockwise arrangement of the oxyalkylene units can be present,

the radicals R 4 are each, independently of one another, R 1 , —R 2 —Si(R 5 ) 3 , R 3 or H,

the radicals R 5 are identical or different alkyl, alkoxy, aryl, aryloxy or alkenyl radicals having from 1 to 20 carbon atoms, preferably a methoxy and/or ethoxy group, with the proviso that at least one R 5 is an alkoxy group,

n is from 1 to 20,

m is from 0 to 20, with m only being 0 when R 4 is the radical —R 2 —Si(R 5 ) 3 and otherwise being ≧1,

o is from 0 to 20,

p is from 1 to 200.

2. The compound as claimed in claim 1 , wherein ≧90% of the radicals R 1 are methyl groups and R 2 is an alkylene radical having from 1 to 5 carbon atoms.

3. The compound as claimed in claim 1 , wherein R 3 is a radical of the general formula (II) in which R 3a is a methyl and/or ethyl radical and R 6a , R 6b are identical or different and are each hydrogen, methyl or ethyl.

4. The compound as claimed in claim 1 , wherein R 3 is a radical of the general formula (II) in which R 3a is a methyl and/or ethyl radical and R 6a , R 6b are identical or different and are each hydrogen, methyl or ethyl, with the proviso that at least one of the radicals is hydrogen.

5. The compound as claimed in claim 1 , wherein R 3 is a radical of the general formula (II) in which the alkoxy radicals

have a block character.

6. The compound as claimed in claim 1 , wherein R 4 is the radical —R 2 —Si(R 5 ) 3 in which R 2 is an alkylene radical having from 1 to 5 carbon atoms and at least one radical R 5 is a methoxy or ethoxy group.

7. The compound as claimed in claim 1 , wherein 1<n a +n b ≦15.

8. The compound as claimed in claim 1 , wherein n, m, o <5 and p=10 to 50, with the proviso that at least one SiH bond and at least one alkoxy group are present in the molecule.

9. An aqueous preparation for the water-repellent impregnation of porous mineral building materials, which comprises

a) from 10 to 80% by weight of compounds as claimed in claim 1 ,

b) from 0.5 to 10% by weight of an emulsifier or emulsifier mixture,

c) from 10 to 89.5% by weight of water and, if desired,

d) from 0 to 0.5% by weight of preservative.

10. The aqueous preparation of claim 9 , wherein ≧90% of the radicals R 1 are methyl groups and R 2 is an alkylene radical having from 1 to 5 carbon atoms.

11. The aqueous preparation of claim 9 , wherein R 3 is a radical of the general formula (II) in which R 3a is a methyl and/or ethyl radical and R 6a , R 6b are identical or different and are each hydrogen, methyl or ethyl.

12. The aqueous preparation of claim 9 , wherein R 3 is a radical of the general formula (II) in which R 3a is a methyl and/or ethyl radical and R 6a , R 6b are identical or different and are each hydrogen, methyl or ethyl, with the proviso that at least one of the radicals is hydrogen.

13. The aqueous preparation of claim 9 , wherein R 3 is a radical of the general formula (II) in which the alkoxy radicals

have a block character.

14. The aqueous preparation of claim 9 , wherein R 4 is the radical —R 2 —Si(R 5 ) 3 in which R 2 is an alkylene radical having from 1 to 5 carbon atoms and at least one radical R 5 is a methoxy or ethoxy group.

15. The aqueous preparation of claim 9 , wherein 1<n a +n b ≦15.

16. The aqueous preparation of claim 9 , wherein n, m, o <5 and p=10 to 50, with the proviso that at least one SiH bond and at least one alkoxy group are present in the molecule.

17. A method of providing a water-repellent surface for a porous mineral building material by impregnating a porous mineral building material with the aqueous preparation of claim 9 .