Appeal No. 2007-3827
Application 08/713,905
brief heating of the reaction product in vacuo below the boiling point of the
solvent used or by blowing a neutral gas through it at high temperature is
sufficient for destroying or otherwise disposing of any carbamic acid
chlorides still present” (id. col. 2, ll. 34-41).
We find Biskup acknowledges that “[a]lthough the preparation of
organic isocyanates from the corresponding amines by reaction with
phosgene in the gas phase has long been known (e.g., Siefken, Ann. 562, 108
(1949)), the process has, until now, only been of technical importance for
monoamines . . . and (cyclo)aliphatic diamines” (Biskup col. 1,
ll. 10-16; emphasis supplied). Thus, Biskup would have disclosed to one of
ordinary skill in the art that the phosgenation of aromatic diamines,
including ether containing aromatic diamines, to the corresponding aromatic
diisocyanates, including ether containing aromatic diisocyanates, in high
yield can be conducted with an excess of phosgene in the vapor phase in
continuous manner with an inert, diluent solvent carrier gas at a temperature
above the boiling point of the diamine with selective recovery and
distillation of the diisocyanate at the same temperature, wherein the
temperature is generally from 200° to 600°C and the process conducted
under pressure (id., e.g., Abstract, col. 1, l. 45, to col., 2, l. 20, col. 2, l. 63, to
col. 3, l. 6, col. 3, l. 50, to col. 5, l. 4, col. 5, ll. 29-31, and Examples 1-3
and 5). The selective recovery is conducted in inert solvent at a temperature
above the decomposition temperature of the carbamic acid chloride
corresponding to the diisocyanate (id., e.g., col. 4, l. 50, to col. 5, l. 4). The
solvents used for phosgenation and product recovery include chlorobenzene,
14
Page: Previous 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Next
Last modified: September 9, 2013