Appeal No. 2007-3827
Application 08/713,905
o-dichlorobenzene, and xylene (id., e.g., col. 3, ll. 1-6, and col. 4, l. 66, to
col. 5, l. 4).
We find Bischof acknowledges that “[p]reparation of organic
isocyanates by reacting amines with phosgene in the gas phase is known.
(See, for example, Siefken, Justus Liebigs Ann. Chem. 562, 108 (1949)),”
and that “such processes have, until now, been recommended only for the
preparation of monoisocyanates . . . [,] commercially available
(cyclo)aliphatic diisocyanates . . . or large-scale production of aromatic
diisocyanates” (Bischof col. 1, ll. 10-18; emphasis supplied). Thus, Bischof
would have disclosed to one of ordinary skill in the art the phosgenation of
aliphatic and cycloaliphatic diamines to the corresponding diisocyanates can
be conducted with an excess of phosgene in the vapor phase in continuous
manner with an inert, diluent carrier gas at a temperature of from 200° to
600° C and under pressure, with selective recovery of the diisocyanate
followed by distillation to obtain the “pure” diisocyanate product in higher
yields than by conventional phosgenation processes (id., e.g., col. 1,
ll. 48-56, col. 2, l. 1, to col. 3, l. 38, col. 4, ll. 12-50, and Examples 1-4). The
selective recovery is conducted in inert solvent at a temperature above the
decomposition temperature of the corresponding to the diisocyanate (id.,
e.g., col. 4, ll. 12-35). The solvents used for phosgenation and product
recovery include chlorobenzene, o-dichlorobenzene, and xylene (id., e.g.,
col. 3, ll. 25-28, and col. 4, ll. 24-30).
We find Joulak acknowledges that the preparation of mono- and
polyisocyanates by phosgenation of amines “in the gaseous phase has long
been known to this art, albeit such reaction has essentially been limited to
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