Mixtures of cyclic branched siloxanes of the D/T type and conversion products thereof

1. A mixture of cyclic branched siloxanes having exclusively D and T units, wherein the cumulative proportion of the D and T units having Si-alkoxy and/or SiOH groups that are present in the siloxane matrix, determinable by 29 Si NMR spectroscopy, is greater than 2 and less than 10 mole percent, wherein the cyclic branched siloxanes do not have any further functional groups.

2. The mixture of cyclic branched siloxanes according to claim 1 , wherein the ratio of D to T units is between 10:1 and 3:1.

3. The mixture of cyclic branched siloxanes having exclusively D and T units according to claim 1 , wherein the molar mass ratio of the mixture M w /M n is in the range of 2<M w /M n <50.

4. The mixture of cyclic branched siloxanes according to claim 1 , wherein the branching T unit derives from alkyltrialkoxysilanes and phenyltrialkoxysilanes.

5. The mixture of cyclic branched siloxanes according to claim 1 , wherein the branching T unit derives from methyltriethoxysilane.

6. The mixture of cyclic branched siloxanes according to claim 1 , dissolved in a silicon-containing solvent.

7. The process for preparing mixtures of cyclic branched siloxanes according to claim 1 , comprising

(a) an acid-catalysed equilibration of trialkoxysilanes with siloxane cycles and/or α,ω-dihydroxypolydimethylsiloxane in the presence of at least one acidic catalyst and then

(b) a hydrolysis and condensation reaction initiated by addition of water, and addition of a silicon-containing solvent, followed by

(c) a distillative removal of the alcohol released, of water present in the system and of silicon-containing solvent, and a neutralization or removal of the acidic catalyst and optionally removal of salts that have possibly formed,

wherein the silicon-containing solvent preferably comprises the isomeric siloxane cycles octamethylcyclotetrasiloxane (D 4 ), decamethylcyclotetrasiloxane (D 5 ) and/or mixtures thereof, advantageously working in mass ratios of silicon-containing solvent to the siloxane having D and T units of from 1:1 to 5:1.

8. The process according to claim 7 , wherein the acidic catalyst used is para-toluenesulfonic acid, trifluoromethanesulfonic acid, trichloroacetic acid, sulfuric acid, perchloric acid, phosphoric acid and/or hexafluorophosphoric acid, in amounts of from 0.1 to 2.0 percent by weight, based in each case on the silicon-containing component of the reaction matrix.

9. The process according to claim 8 , wherein the reaction is conducted at temperatures in the range from 20° C. to 120° C.

10. The process according to claim 7 , wherein the acidic catalyst used is a macrocrosslinked ion exchange resin containing sulfonic acid groups in amounts of from 1.0 to 10.0 percent by weight based in each case on the silicon-containing component of the reaction matrix.

11. The process according to claim 7 , wherein an at least 150% H 2 O excess is used, based on the groups to be condensed.

12. The process according to claim 1 , wherein the reaction comprises a preliminary equilibration step at temperatures of T>40° C., followed by a condensation initiated by addition of water at temperatures of T>60° C., where the water is added in one portion, in several portions or continuously.

13. The process for preparing branched organomodified siloxanes, wherein

in a first step mixtures of cyclic branched siloxanes are provided according to claim 1 ,

and

in a second step the mixtures of cyclic branched siloxanes are equilibrated under acidic conditions with silanes and/or siloxanes.

14. The process according to claim 13 , wherein the silanes and/or siloxanes used are acid-equilibratable silicon compounds,

wherein the silanes are selected from the group consisting of diethoxydimethylsilane, trimethylalkoxysilanes and dimethyldichlorosilane,

and/or

wherein the siloxanes are selected from the group consisting of tetramethyldisiloxane, α,ω-dihydropolydimethylsiloxanes, poly(methylhydro)siloxanes, α,ω-dialkoxypolydimethylsiloxanes and α,ω-divinylpolydimethylsiloxanes.

15. The process according to claim 13 , wherein, in the second step in which the mixtures of cyclic branched siloxanes are acid-equilibrated with silanes and/or siloxanes,

a) an amount of ≥0.2% by weight of acidic catalyst,

b) the preferably time-limited application of an auxiliary vacuum in the equilibration step lowers the concentration of the groups capable of condensation, where the auxiliary vacuum is ≤200 mbar, and/or

c) there is sequenced addition of the acidic catalyst, the sequenced addition preferably being effected in 2 steps, and/or

d) steps (b) and (c) are combined.

16. The process according to claim 13 , wherein in the second step in which the mixtures of cyclic branched siloxanes are acid-equilibrated with silanes and/or siloxanes, the equilibration is undertaken over a water-containing macroporous polystyrene resin containing sulfonic acid groups, which is used in amounts of 3% to 9% by weight and which has been wetted with 8% to 12% by weight of water, and the specific surface area of which is ≥35 m 2 /g and the mean pore diameter of which is at least 65 nm.

17. The process for preparing branched silicone oils, wherein in a first step cyclic branched siloxanes are provided, according to claim 1 , and in a second step the cyclic branched siloxanes are reacted with polydimethylsiloxanes or hexamethyldisiloxane.

18. The mixture of cyclic branched siloxanes according to claim 1 , wherein the cumulative proportion of the D and T units having Si-alkoxy and/or SiOH groups that are present in the siloxane matrix, determinable by 29 Si NMR spectroscopy, is less than 9 mole percent.

19. The mixture of cyclic branched siloxanes according to claim 1 , wherein the ratio of D to T units is between 6:1 and 4:1.

20. The mixture of cyclic branched siloxanes having exclusively D and T units according to claim 1 , dissolved in isomeric siloxane cycles octamethylcyclotetrasiloxane D 4 , decamethylcyclotetrasiloxane D 5 or mixtures thereof.