Mixtures of cyclic branched siloxanes of the D/T type and conversion products thereof
Mixtures of cyclic branched siloxanes having exclusively D and T units and having no functional groups, with the proviso that 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 ≤2 mole percent, are described, as are branched organomodified siloxanes obtainable therefrom.
1. A process for preparing a mixture of cyclic branched siloxanes having exclusively D and T units and having no functional groups, 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 ≤2 mole percent, wherein the ratio of the D and T units is between 10:1 and 3:1, and wherein a trialkoxysilane in a solvent is reacted with siloxane cycles or α,ω-dihydroxypolydimethylsiloxane with addition of water and in the presence of at least one acidic catalyst wherein the solvent is selected from the group consisting of toluene, cyclohexane, and ethyl carbonate in mass ratio of solvent to the siloxane of from 1:1 to 5:1, and wherein the process 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.
2. The process according to claim 1 , wherein the solvent is cyclohexane.
3. The process according to claim 1 , wherein the acidic catalyst used is
(a) selected from the group consisting of para-toluenesulfonic acid, trifluoromethanesulfonic acid, trichloroacetic acid, sulfuric acid, perchloric acid, phosphoric acid and 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,
or
(b) 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.
4. The process according to claim 3 , wherein the acidic catalyst used is
(a) selected from the group consisting of para-toluenesulfonic acid, trifluoromethanesulfonic acid, trichloroacetic acid, sulfuric acid, perchloric acid, phosphoric acid and hexafluorophosphoric acid, in amounts of from 0.15 to 1.0 percent by weight.
5. The process according to claim 1 , wherein the reaction is conducted at temperatures in the range from 10° C. to 150° C. and wherein the ratio of the D and T units is between 6:1 and 4:1.
6. The process according to claim 1 , wherein the reaction is conducted at temperatures in the range from 40° C. to 110° C.
7. The process for preparing a mixture of cyclic branched siloxanes having exclusively D and T units and having no functional groups, wherein the ratio of the D and T units is between 10:1 and 3:1, and 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 ≤2 mole percent, and wherein a trialkoxysilane in a solvent is reacted with siloxane cycles or α,ω-dihydroxypolydimethylsiloxane with addition of water and in the presence of at least one acidic catalyst.
8. The process according to claim 7 , 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.
9. The process for preparing branched organomodified siloxanes, wherein
in a first step mixtures of cyclic branched siloxanes are provided, according to claim 7 ,
and
in a second step the mixtures of cyclic branched siloxanes are equilibrated under acidic conditions with silanes and siloxanes.
10. The process according to claim 9 , wherein the silanes and siloxanes used are any acid-equilibratable silicon compounds, the silanes are selected from the group consisting of diethoxydimethylsilane, methyltriethoxysilane, trimethylalkoxysilane, and dimethyldichlorosilane, and the siloxanes selected from the group consisting of tetramethyldisiloxane, decamethylcyclopentasiloxane, α,ω-dihydropolydimethylsiloxanes, poly(methylhydro)siloxanes, α,ω-dialkoxypolydimethylsiloxanes or α,ω-divinylpolydimethylsiloxanes.
11. The process for preparing branched silicone oils, wherein in a first step mixtures of cyclic branched siloxanes are provided, according to claim 7 ,
and in a second step the cyclic branched siloxanes are reacted with polydimethylsiloxanes or hexamethyldisiloxane.