Process for preparing silicone polyethers

1. A process for preparing a silicone polyether comprising reacting;

(A) a polyether having at least one terminally unsaturated aliphatic hydrocarbon group and an alkali metal content of less than 50 ppm,

(B) an organohydrogensiloxane having an acid number of less than 0.005, via a hydrosilylation reaction.

2. The process of claim 1 wherein the silicone polyether has a —SiOC— content of less than 1 mole percent.

3. The process of claim 1 wherein the polyether (A) has the average formula

R 1 O(C n H 2n O) m R 2 ,

where n is from 2 to 4 inclusive,

m is greater than 2,

R 1 is an unsaturated aliphatic hydrocarbon,

R 2 is R 1 , hydrogen, an acetyl group, or a monovalent hydrocarbon containing 1 to 8 carbons.

4. The process of claim 3 where

n =2, R 1 is an allyl group, and R 2 is hydrogen.

5. The process of claim 1 wherein the organohydrogensiloxane is selected from an organopolysiloxane comprising the average formula;

(R 2 HSiO 0.5 )(SiO 2 ) w (R 2 HSiO 0.5 )

(R 2 HSiO 0.5 )(SiO 2 ) w (R 2 SiO) x (R 2 HSiO 0.5 )

(R 2 HSiO 0.5 )(R 2 SiO) x (R 2 HSiO 0.5 )

(R 3 SiO 0.5 )(R 2 SiO) x (RHSiO) y (R 3 SiO 0.5 )

(R 3 SiO 0.5 )(R 2 SiO) x (HRSiO) y (RSiO 1.5 ) z (R 3 SiO 0.5 )

(R 3 SiO 0.5 )(R 2 SiO) x (RHSiO) y (SiO 2 ) w (R 3 SiO 0.5 )

where R is an organic group,

w≧0, x≧0, y≧1, and z is ≧0.

6. The process of claim 5 wherein the organohydrogensiloxane is a dimethyl, methyl-hydrogen polysiloxane having the formula;

(CH 3 ) 3 SiO[(CH 3 ) 2 SiO] x [(CH 3 )HSiO] y Si(CH 3 ) 3 or

(CH 3 ) 2 HSiO[(CH 3 ) 2 SiO] x SiH(CH 3 ) 2

where x≧0 and y≧2.

7. The process of claim 1 wherein the hydrosilylation reaction is catalyzed by a platinum compound.

8. The process of claim 1 where the molar ratio of the unsaturated groups of the polyether A) to the SiH content of the organohydrogensiloxane B) is greater than one.

9. The process of claim 8 wherein the polyether A) has the formula

H 2 C═CHCH 2 O(C 2 H 4 O) a H

where a is greater than 2,

and organohydrosiloxane B) has the average formula

(CH 3 ) 3 SiO[(CH 3 ) 2 SiO] x [(CH 3 )HSiO] y Si(CH 3 ) 3

where x≧0 and y≧1.

10. The process according to claims 1 wherein greater than 99.5 mole % of the SiH of the organohydrosiloxane reacts in the hydrosilylation reaction.

11. The process according to claims 1 wherein the hydrosilylation reaction occurs in a continuous process.

12. The process according to claim 11 wherein the continuous process occurs in a plug flow reactor.