Water repellent for concrete

1. A water repellent composition for treating porous substrates comprising an emulsion which includes water, at least one surfactant, and a siloxane copolymer having the formula

wherein R is an alkyl radical having 1 to 3 carbon atoms; a has a value of from 1 to 12; R′ is an alkyl radical having 6 to 12 carbon atoms; b≧2; (a+b) is at least 5; and being substantially free of alkenes;

wherein the siloxane copolymer is obtained by reacting an alkene with a linear siloxane containing silicon hydrogen groups at a molar ratio of alkene to SiH groups of at least 0.25:1; wherein the siloxane copolymer is vacuum stripped; and

wherein the composition has a Volatile Organic Content according to ASTM D 5095 below 100 g/l.

2. The composition of claim 1 in which R is a methyl radical (Me).

3. The composition of claim 2 in which the siloxane copolymer is partially or completely hydrolyzed to the corresponding silanol.

4. The composition of claim 2 in which b≧a/2.

5. The composition of claim 2 in which (a+b)≧6, alternatively in which (a+b)≧8.

6. The composition of claim 1 in which the siloxane copolymer is partially or completely hydrolyzed to the corresponding silanol.

7. The composition of claim 1 in which b≧a/2.

8. The composition of claim 1 in which (a+b)≧6.

9. The composition of claim 1 in which (a+b)≧8.

10. The composition according to claim 1 in which the composition has a Volatile Organic Content according to ASTM D 5095 below 50 g/l.

11. A process to improve water repellency of a finished substrate by applying the composition according to claim 1 to the finished substrate.

12. The process according to claim 11 where the substrate is concrete or reinforced concrete.

13. The process according to claim 11 where the substrate is masonry, cement, stucco, natural or artificial stone, ceramic, terracotta bricks, plaster board, fibre cement board, other cement containing products, wood particle board, wood plastic composite, oriented strand board, or wood.

14. A process to improve water repellency of a substrate by including the composition according to claim 1 in starting materials before or during manufacture of the substrate.

15. A process of preparing an emulsion by:

1) reacting an alkene with a linear siloxane containing silicon hydrogen groups at a molar ratio of alkene to SiH groups of at least 0.25:1 to provide a siloxane copolymer having the formula

wherein R is an alkyl radical having 1 to 3 carbon atoms; a has a value of from 1 to 12; R′ is an alkyl radical having 6 to 12 carbon atoms; b has a value of at least 2; and (a+b) is at least 5;

2) vacuum stripping the siloxane copolymer;

3) combining

i) water,

ii) the siloxane copolymer having the formula

 and

iii) a surfactant;

4) homogenizing the combined components to form an emulsion; and

5) optionally admixing additional water and additional ingredient;

wherein the emulsion is substantially free of alkenes and the emulsion has a Volatile Organic Content according to ASTM D 5095 below 100 g/l.