Ex Parte Pohl et al

Patent Trial and Appeal Board

Dec 12, 2012

12313469 (P.T.A.B. Dec. 12, 2012)

UNITED STATES PATENT AND TRADEMARK OFFICE
__________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
__________

Ex parte FRITZ POHL, KLAUS BISKUP, RAINER BRUNS,
FRIEDHELM STEFFENS, and LARS PADEKEN
__________

Appeal 2012-002400
Application 12/313,469
Technology Center 1600
__________

Before ERIC GRIMES, STEPHEN WALSH, and
JACQUELINE WRIGHT BONILLA, Administrative Patent Judges.

WALSH, Administrative Patent Judge.

DECISION ON APPEAL
This is an appeal under 35 U.S.C. § 134(a) from the rejection of
claims directed to a process for the production of a primary aromatic
diisocyanate in gaseous phase. The Patent Examiner rejected the claims for
obviousness. We have jurisdiction under 35 U.S.C. § 6(b). We reverse.
Appeal 2012-002400
Application 12/313,469

2
STATEMENT OF THE CASE
“The reaction of aromatic diamines with phosgene in the gaseous
phase to form the corresponding diisocyanates is … described in the
literature.” (Spec. 2, ll. 14-15.) According to the Specification, “[t]here
have been a number of attempts to minimize the formation of solids,
particularly in the reaction of aromatic diamines with phosgene in the
gaseous phase, in order to allow an industrial scale phosgenation of aromatic
diamines in the gaseous phase.” (Id. at 3, ll. 1-4.) The Summary of the
Invention tells us:
Surprisingly this object has been achieved by (1) reacting phosgene
and the primary aromatic diamine(s) within a mean, hydrodynamic
residence time of from 0.05 to 15 seconds and (2) using primary
aromatic diamine(s) containing overall less than 0.05 mole % of
aliphatic amine(s) per mole of primary amino groups and (3) ensuring
that no keto groups are present in any aliphatic amine which may be
present. It is aliphatic amines containing no keto groups which are
believed to be largely responsible for the formation of solid deposits
in the gas phase phosgenation.

(Id. at 6, ll. 19-26, emphasis added.)
Claims 1-15 are on appeal. Claim 1 is representative and reads as
follows:
1. A process for the production of a primary aromatic diisocyanate
comprising reacting a primary aromatic diamine with phosgene in gaseous
phase in which
a) the phosgene and the primary aromatic diamine are reacted
within a mean residence time of 0.05 to 15 seconds, and
b) the primary aromatic diamine contains less than 0.05 mole %
overall of aliphatic amine containing no keto groups per mole
of primary amino groups.

Appeal 2012-002400
Application 12/313,469

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The Examiner rejected claims 1-15 under 35 U.S.C. § 103(a) as
unpatentable over Biskup,
1
Applicants’ acknowledgment of prior art at
Specification 8, and Koch.
2

OBVIOUSNESS
The Examiner cited Biskup’s process for producing a primary
aromatic diisocyanate by reacting a primary aromatic diamine with phosgene
in the gaseous phase. (Office action 3, quoting Biskup col. 3, l. 50 through
col. 4, l. 20.)
3
The Examiner found that the only differences between
Biskup’s process and Appellants’ process are:
(i) Biskup et al fail to teach the primary aromatic diamine contains
less than 0.05 mole% overall of aliphatic amine containing no keto
groups per mole of primary amino groups;
(ii) Biskup et al fails to teach the process is carried out adiabatically.

(Id. at 4.) As evidence that feature (i) was known in the art, the Examiner
relied on Applicants’ acknowledgement of prior art at Specification 8. (Id.)
As evidence that feature (ii), adiabatic phosgenation, was known in the art
and would have been an obvious modification of Biskup’s process, the
Examiner cited Koch’s use of adiabatic conditions for preparing isocyanates
by reacting primary amines with phosgene. (Id., citing Koch ¶¶[0009] and
[0010].)
Appellants contend that the prior art discussed at Specification page 8
did not suggest that the diamine composition to be phosgenated should be

1
Klaus Biskup et al., US 5,449,818, issued Sept. 12, 1995.
2
Daniel Koch et al., US 2006/0025556 A1, published Feb. 2, 2006.
3
Citations are to the Office action mailed Aug. 5, 2010, because the copy of
the rejection pasted into the Answer is illegible.
Appeal 2012-002400
Application 12/313,469

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controlled to ensure that it contained less than 0.05 mole% aliphatic amine
containing no keto groups. (App. Br. 4.) We agree with Appellants. In
pertinent part, the Specification states:
The low content of aliphatic amines containing no keto groups in the
aromatic diamines to be reacted in the desired gas phase phosgenation
which is required in the present invention is all the more surprising
because simultaneous phosgenation of aliphatic and aromatic primary
amino groups is taught in the prior art. (See, e.g., DE-A 2249459, DE-
A- 198 28 510). Although the literature deals with the stability of the
amines used in a gas phase phosgenation regarding their
decomposition under de-amination, no information on the necessary
relative stability of the formed isocyanates by the simultaneous use of
both aromatic and (cyclo)aliphatic primary amino groups can be
derived from the specified vaporization and reaction conditions. In
particular, the prior art does not give any indication that the aliphatic
amines containing no keto groups are a problem.

(Spec. 8, ll. 5-15, emphasis added.) Nothing in this paragraph is an
admission that it was known to keep aliphatic amines with no keto groups
below a certain level.
The Examiner reasoned: “Since Biskup et al also did not get any
solid formation in their process, the amount of aliphatic amine is expected to
be extremely low or the reactant is free from the aliphatic amine.” (Final
Rej. 3.) First, the possibility that Biskup’s reactant was free of aliphatic
amine is only a possibility. “Inherency . . . may not be established by
probabilities or possibilities. The mere fact that a certain thing may result
from a given set of circumstances is not sufficient.” In re Robertson,
169 F.3d 743, 745 (Fed. Cir. 1999) (citations omitted). Second, Appellants
rebut the Examiner’s reasoning by citing “the express teaching of Biskup et
al that solid formation is avoided by keeping the contact time between
phosgene and aromatic diamine short at column 1, lines 45-52.” (App. Br.
Appeal 2012-002400
Application 12/313,469

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5.) The evidence supports Appellants’ point, as Biskup taught “it is possible
to prepare aromatic diisocyanates while avoiding solid substances which
block up the reactors . . . if the contact between phosgene and aromatic
diamine is kept within a very narrowly restricted contact time….” (Biskup,
col. 1, ll. 45-52.)
Appellants contend their comparative examples demonstrate “a
significant improvement with respect to solid deposition.” (App. Br. 3.)
The Specification’s “Example 1” describes a run in which the diamine
mixture used was composed of 2,4- and 2,6-toluenediamine containing
overall 0.01 mole % of aliphatic amines containing no keto groups, per
mole, of primary amino groups. The result:
After an operating time of 300 hours, the differential pressure was 28
mbar and was thus unchanged within the limits of the measurement
accuracy of industrial measuring instruments. An inspection showed
no deposits of solids.

(Spec. 17, ll. 24-26.) In contrast, the Specification’s “Example 2
(Comparative)” describes a run in which the diamine mixture used was
composed of 2,4- and 2,6-toluenediamine containing 0.07 mole % overall of
aliphatic amines containing no keto groups, per mole of primary amino
groups. The result:
After an operating time of 30 hours, the pressure in the gaseous TDA
line rose significantly and the differential pressure between the TDA
line and the outlet of the condensation stage was 3177 mbar. The
reaction therefore had to be discontinued. An inspection revealed very
large deposits of solids.

(Id. at 18, ll.18-21.) We agree with Appellants that the prior art of record
did not suggest these results.

Appeal 2012-002400
Application 12/313,469

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CONCLUSION OF LAW
The prior art of record did not teach or suggest producing aromatic
diisocyanate by using a primary aromatic diamine containing less than 0.05
mole % overall of aliphatic amine containing no keto groups per mole of
primary amino groups.

SUMMARY
We reverse the rejection of claims 1-15 under 35 U.S.C. § 103(a) as
unpatentable over Biskup, Applicants’ acknowledgment of prior art at
Specification 8, and Koch.

REVERSED

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