Siloxane bischloroformates
View Patent ↗Siloxane bischloroformates are prepared in a continuous process by phosgenating siloxane bisphenols in a flow reactor using a substantial excess of phosgene and sodium hydroxide. While very high levels (>95%) of conversion of the siloxane bisphenol to the corresponding siloxane bischloroformate are achieved using a flow reactor according to the method of the invention, only more modest conversion (˜90%) of the siloxane bisphenol to the corresponding siloxane bischloroformate is attained when analogous batch processes are employed. The process holds promise for use in the manufacture of silicone-containing copolycarbonates which requires high purity siloxane bischloroformate intermediates.
1. A siloxane bischloroformate comprising structure IX and comprising fewer than 10 percent hydroxy endgroups
wherein R 1 is independently at each occurrence a C 1 -C 10 alkylene group optionally substituted by one or more C 1 -C 10 alkyl or aryl groups, an oxygen atom, an oxyalkyleneoxy moiety
—O—(CH 2 ) t —O—,
or an oxyalkylene moiety
—O—(CH 2 ) t —,
where t is an integer from 2-20;
R 2 and R 3 are each independently at each occurrence, halogen, C 1 -C 6 alkoxy, C 1 -C 6 alkyl, or C 6 -C 10 aryl;
z and q are independently integers from 0-4;
R 4 , R 5 , R 6 and R 7 are each independently at each occurrence C 1 -C 6 alkyl, aryl, C 2 -C 6
alkenyl, trifluoropropyl, or styrenyl; and
p is an integer from 1 to about 100.
2. A siloxane bischloroformate comprising structure VIII
wherein p is an integer between 1 and about 100, said siloxane bischloroformate comprising fewer than 10 percent hydroxy endgroups.
3. A siloxane bischloroformate according to claim 1 comprising fewer than 5 percent hydroxy endgroups.
4. A siloxane bischloroformate according to claim 3 comprising fewer than 1 percent hydroxy endgroups.
5. A siloxane bischloroformate according to claim 1 less than about 0.5 percent carbonate groups.
6. A siloxane bischloroformate according to claim 5 comprising fewer than 5 percent hydroxy endgroups.
7. A siloxane bischloroformate according to claim 6 comprising fewer than 1 percent hydroxy endgroups.
8. A siloxane bischloroformate according to claim 1 wherein p is an integer from 20 to about 100.
9. A siloxane bischloroformate according to claim 1 wherein p has an average value of about 50.
10. A siloxane bischloroformate according to claim 2 comprising fewer than 5 percent hydroxy endgroups.
11. A siloxane bischloroformate according to claim 10 comprising fewer than 1 percent hydroxy endgroups.
12. A siloxane bischloroformate according to claim 2 less than about 0.5 percent carbonate groups.
13. A siloxane bischloroformate according to claim 12 comprising fewer than 5 percent hydroxy endgroups.
14. A siloxane bischloroformate according to claim 13 comprising fewer than 1 percent hydroxy endgroups.
15. A siloxane bischloroformate according to claim 2 wherein p is an integer from 20 to about 100.
16. A siloxane bischloroformate according to claim 2 wherein p has an average value of about 50.