Method for producing phosphonatosilanes
In the preparation of phosphonatosilanes by reaction of organophosphites with halocarbon-functional silanes, the safety of the reaction is markedly increased while increasing space/time yield by continuously or periodically withdrawing reaction mixture, freeing the withdrawn mixture of phosphonatosilane product, and recycling the product-depleted remainder back to the reaction. Operation at temperatures of 100° C. or lower is made possible by this process.
1. A process for preparing phosphonatosilanes of the formula (II)
R 1 n (X) 3-n —Si—R 3 —PO(OR 4 )(OR 5 ) (II)
comprising reacting halogenated silanes of the formula (III)
R 1 n (X) 3-n —Si—R 3 —Hal (III)
with phosphites of the formula (IV)
P(OR 4 )(OR 5 )(OR 6 ) (IV)
in a reaction vessel,
where
R 1 is an optionally halogen-substituted hydrocarbon radical having 1-20 carbon atoms or hydrogen,
X is a hydrolyzable group or OH,
R 3 is an optionally halogen-substituted alkylene radical having 1-10 carbon atoms,
R 4 , R 5 and R 6 are each optionally halogen-substituted hydrocarbon radicals having 1-20 carbon atoms,
Hal is a halogen atom and
n is 0, 1, 2 or 3,
in which a portion of the reaction mixture is withdrawn continuously or repeatedly during the reaction, separating the product formed from the reactants by applying the reaction mixture to a thin-film evaporator, separating a bottoms high boiler fraction containing product, and recycling distillate to the reaction vessel.
2. The process of claim 1 , wherein R 1 is an alkyl radical having from 1 to 3 carbon atoms or hydrogen.
3. The process of claim 1 , wherein R 3 is selected from the group consisting of methylene, ethylene, and n-propylene.
4. The process of claim 2 , wherein R 3 is selected from the group consisting of methylene, ethylene, and n-propylene.
5. The process of claim 1 , wherein R 4 , R 5 and R 6 are each an alkyl radical having from 1 to 6 carbon atoms or a phenyl.
6. The process of claim 2 , wherein R 4 , R 5 and R 6 are each an alkyl radical having from 1 to 6 carbon atoms or a phenyl.
7. The process of claim 3 , wherein R 4 , R 5 and R 6 are each an alkyl radical having from 1 to 6 carbon atoms or a phenyl.
8. The process of claim 1 , wherein each X independently is an alkoxy group having from 1 to 3 carbon atoms, or is fluorine, chlorine or bromine.
9. The process of claim 2 , wherein each X independently is an alkoxy group having from 1 to 3 carbon atoms, or is fluorine, chlorine or bromine.
10. The process of claim 3 , wherein each X independently is an alkoxy group having from 1 to 3 carbon atoms, or is fluorine, chlorine or bromine.
11. The process of claim 5 , wherein each X independently is an alkoxy group having from 1 to 3 carbon atoms, or is fluorine, chlorine or bromine.
12. The process of claim 1 , in which reaction mixture is withdrawn continuously.
13. The process of claim 1 , in which the entire process is conducted continuously.
14. The process of claim 1 , which is conducted at a temperature below 200° C. and at a pressure where halocarbon R 4 -Hal volatizes from the reaction mixture.
15. The process of claim 1 , which is conducted at a temperature at about 100° C. or lower and at a pressure where halocarbon R 4 -Hal volatizes from the reaction mixture.