Method for producing siloxanes from alkali salts of silanols
Cyclic siloxanes are prepared economically by reaction of an alkali metal siliconate having a mol ratio of alkali metal cation to silicon of less than one or their hydrolysis/condensation products or mixture thereof, with a halosilane.
1. A process for preparing cyclic siloxanes of the formula (1)
[RSi(OSiR 1 R 2 R 3 )O] n (1),
comprising:
reacting alkali metal salts of silanols of the formula (2),
R—Si(OH) 3-m (OM) m (2),
wherein m is 0, 1, 2, or 3, and over all species of the alkali metal salts of silanols of the formula (2), m is on average 0.1 to <1,
their hydrolysis/condensation products, or alkali metal salts of silanols of the formula (2) together with their hydrolysis/condensation products, wherein the molar ratio of cation M to silicon is <1,
with halosilanes of the formula (3)
R 1 R 2 R 3 Si-Hal (3)
where
n is 3, 4, 5, 6, 7 or 8,
R is an organic radical bonded via carbon to silicon,
M is an alkali metal cation,
Hal is a halogen radical, and
R 1 , R 2 , and R 3 are hydrogen, C 1-10 alkoxy radicals, C 1-20 aryloxy radicals or monovalent hydrocarbon radicals having 1 to 18 carbon atoms which are unsubstituted or substituted by halogen atoms or alkoxy groups,
and thereby producing cyclic siloxanes of the formula (1).
2. The process of claim 1 , wherein R is a monovalent, Si—C-bonded hydrocarbon radical having 1 to 30 carbon atoms, which is unsubstituted or substituted by halogen atoms, C 1-6 alkyl or C 1-6 alkoxy groups or silyl groups, and in which one or more mutually nonadjacent —CH 2 — units are optionally replaced by —O— or —S—.
3. The process of claim 1 , wherein M comprises sodium, potassium, or a mixture thereof.
4. The process of claim 2 , wherein M comprises sodium, potassium, or a mixture thereof.
5. The process of claim 1 , wherein the molar ratio M:Si in formula (2) is from 0.4 to 0.85.
6. The process of claim 2 , wherein the molar ratio M:Si in formula (2) is from 0.4 to 0.85.
7. The process of claim 3 , wherein the molar ratio M:Si in formula (2) is from 0.4 to 0.85.
8. The process of claim 1 , wherein the halosilanes of formula (3) are chlorosilanes.
9. The process of claim 2 , wherein the halosilanes of formula (3) are chlorosilanes.
10. The process of claim 3 , wherein the halosilanes of formula (3) are chlorosilanes.
11. The process of claim 5 , wherein the halosilanes of formula (3) are chlorosilanes.
12. The process of claim 1 , wherein reacting is carried out at 0° C. to 120° C.
13. The process of claim 2 , wherein reacting is carried out at 0° C. to 120° C.
14. The process of claim 3 , wherein reacting is carried out at 0° C. to 120° C.
15. The process of claim 5 , wherein reacting is carried out at 0° C. to 120° C.
16. The process of claim 8 , wherein reacting is carried out at 0° C. to 120° C.
17. The process of claim 1 , wherein reacting is carried out without auxiliary base.
18. The process of claim 2 , wherein reacting is carried out without auxiliary base.
19. The process of claim 3 , wherein reacting is carried out without auxiliary base.
20. The process of claim 5 , wherein reacting is carried out without auxiliary base.
21. The process of claim 1 , wherein n is 4.