Process for producing acetoxy-bearing siloxanes

1. A process for producing trifluoromethanesulfonic acid-acidified, end-equilibrated, acetoxy-bearing siloxanes, wherein the process comprises

reacting cyclic siloxanes, comprising D 4 and/or D 5 ,

and/or mixtures of cyclic branched siloxanes of the D/T type with acetic anhydride

using trifluoromethanesulfonic acid as catalyst and with addition of acetic acid.

2. The process according to claim 1 , wherein the process comprises adding acetic acid in amounts of 0.4 to 3.5 percent by weight, based on the reaction matrix consisting of acetic anhydride and cyclic siloxanes comprising D 4 and/or D 5

or consisting of acetic anhydride and mixtures of cyclic branched siloxanes of the D/T type

or consisting of cyclic siloxanes comprising D 4 and/or D 5 and mixtures of cyclic branched siloxanes of the D/T type.

3. The process according to claim 2 , wherein the reaction is carried out in a temperature range of from 140° C. to 160° C. and over a duration of from 4 to 8 hours.

4. The process according to claim 1 , wherein mixtures of cyclic branched siloxanes of the D/T type consisting of siloxanes comprising D and T units and whose 29 Si NMR spectroscopy-determinable cumulative proportion of D and T units comprising Si-alkoxy and/or SiOH groups present in a siloxane matrix, and contain at least 5 percent by weight of cyclic siloxanes.

5. The process according to claim 4 , wherein the reaction is carried out in a temperature range of 140° C. to 160° C. and over a duration of from 4 to 8 hours.

6. The process according to claim 1 , wherein mixtures of cyclic branched siloxanes comprising exclusively D and T units whose 29 Si NMR spectroscopy-determinable cumulative proportion of D and T units comprising Si-alkoxy and/or SiOH groups present in a siloxane matrix.

7. The process according to claim 1 , wherein trifluoromethanesulfonic acid is employed in amounts of 0.1 to 1.0 percent by mass, based on the reaction matrix consisting of acetic anhydride and cyclic siloxanes comprising D 4 and/or D 5 ,

and/or mixtures of cyclic branched siloxanes of the D/T type.

8. The process according to claim 1 , wherein the reaction is carried out in a temperature range of 140° C. to 160° C. and over a duration of 4 to 8 hours.

9. A trifluoromethanesulfonic acid-acidified, end-equilibrated linear α,ω-acetoxy-bearing siloxane produced by a process according to claim 1 , wherein the trifluoromethanesulfonic acid-acidified, end-equilibrated linear α,ω-acetoxy-bearing siloxane have total cycles contents defined as the sum of the content fractions of the cyclic siloxanes comprising D 4 , D 5 and D 6 based on a siloxane matrix and determined by gas chromatography after their derivatization to afford the corresponding linear α,ω-isopropoxysiloxanes of less than 13% by weight.

10. The trifluoromethanesulfonic acid-acidified, end-equilibrated linear α,ω-acetoxy-bearing siloxane of claim 9 wherein the trifluoromethanesulfonic acid-acidified, end-equilibrated linear α,ω-acetoxy-bearing siloxane have total cycles contents defined as the sum of the content fractions of the cyclic siloxanes comprising D 4 , D 5 and D 6 based on a siloxane matrix and determined by gas chromatography after their derivatization to afford the corresponding linear α,ω-isopropoxysiloxanes of less than 12% by weight.

11. A trifluoromethanesulfonic acid-acidified, end-equilibrated branched acetoxy-bearing siloxane produced by a process according to claim 1 , wherein the trifluoromethanesulfonic acid-acidified, end-equilibrated branched acetoxy-bearing siloxane has total cycles contents defined as the sum of the content fractions of the cyclic siloxanes comprising D 4 , D 5 and D 6 based on a siloxane matrix and determined by gas chromatography after their derivatization to afford the corresponding branched isopropoxysiloxanes of less than 8% by weight.

12. The process according to claim 1 , wherein the process comprises adding acetic acid in amounts of 0.5 to 3 percent by weight, based on the reaction matrix consisting of acetic anhydride and cyclic siloxanes comprising D 4 and/or D 5

or consisting of acetic anhydride and mixtures of cyclic branched siloxanes of the D/T type

or consisting of cyclic siloxanes comprising D 4 and/or D 5 and mixtures of cyclic branched siloxanes of the D/T type.

13. The process according to claim 1 , wherein the process comprises adding acetic acid in amounts of 0.8 to 1.8 percent by weight, based on the reaction matrix consisting of acetic anhydride and cyclic siloxanes comprising D 4 and/or D 5

or consisting of acetic anhydride and mixtures of cyclic branched siloxanes of the D/T type

or consisting of cyclic siloxanes comprising D 4 and/or D 5 and mixtures of cyclic branched siloxanes of the D/T type.

14. The process according to claim 1 , wherein the process comprises adding acetic acid in amounts of 1.0 to 1.5 percent by weight, based on the reaction matrix consisting of acetic anhydride and cyclic siloxanes comprising D 4 and/or D 5

or consisting of acetic anhydride and mixtures of cyclic branched siloxanes of the D/T type

or consisting of cyclic siloxanes comprising D 4 and/or D 5 and mixtures of cyclic branched siloxanes of the D/T type.

15. The process according to claim 1 , wherein mixtures of cyclic branched siloxanes of the D/T type consisting of siloxanes comprising D and T units and whose 29 Si NMR spectroscopy-determinable cumulative proportion of D and T units comprising Si-alkoxy and/or SiOH groups present in a siloxane matrix, and which contain at least 5 percent by weight of octamethylcyclotetrasiloxane (D 4 ), decamethylcyclopentasiloxane (D 5 ) or mixtures thereof, are employed.

16. The process according to claim 1 , wherein trifluoromethanesulfonic acid is employed in amounts of 0.1 to 0.3 percent by mass, based on the reaction matrix consisting of acetic anhydride and cyclic siloxanes comprising D 4 and/or D 5 , and/or mixtures of cyclic branched siloxanes of the D/T type.