Ex Parte Keggenhoff et al

Patent Trial and Appeal Board

Aug 11, 2014

12851604 (P.T.A.B. Aug. 11, 2014)

UNITED STATES PATENT AND TRADEMARK OFFICE
__________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
__________

Ex parte BERTHOLD KEGGENHOFF,
HEINRICH LOKUM, and MATTHIAS BOHM

__________

Appeal 2012-001720
Application 12/851,604
Technology Center 1600
__________

Before ERIC B. GRIMES, JEFFREY N. FREDMAN, and
TINA E. HULSE, Administrative Patent Judges.

FREDMAN, Administrative Patent Judge.

DECISION ON APPEAL
This is an appeal1 under 35 U.S.C. § 134 involving claims to a process
for the production of diisocyanates and polyisocyanates of diphenylmethane.
The Examiner rejected the claims as obvious. We have jurisdiction under
35 U.S.C. § 6(b). We affirm.

1 Appellants identify the Real Party in Interest as Bayer
MaterialScience AG (see App. Br. 1).
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Statement of the Case
Background
The Specification teaches “a process for the production of isocyanates
using solvent recirculation, in which the formation of by-products and thus
the losses of yield and quality impairment of the isocyanate produced are
minimized” (Spec. 2, ll. 23–26).
The Claims
Claims 1, 2, 4, and 5 are on appeal. Claim 1 is representative and
reads as follows (emphasis added):
1. A process for the production of diisocyanates and
polyisocyanates of diphenylmethane comprising:
a) producing a solution of a diamine and/or polyamine
of diphenylmethane in a solvent,
b) producing a solution of phosgene in the same
solvent used to produce the amine solution of a), and
c) combining the solution of amine produced in a) and
the solution of phosgene produced in b),
d) reacting the amine in the solution of amine
produced in a) with the phosgene in the solution of phosgene
produced in b) to form an isocyanate-containing reaction
solution comprising diisocyanates and/or polyisocyanates of
diphenylmethane,
e) separating hydrogen chloride and excess phosgene
from the isocyanate-containing reaction solution to obtain a
crude isocyanate solution,
f) distilling the crude isocyanate solution to separate
the crude isocyanate solution into
(1) an isocyanate-containing stream and
(2) a solvent-containing stream containing from
100 to 1000 ppm of residual phosgene and less than
100 ppm diisocyanate(s) of diphenylmethane,
g) purifying the solvent-containing stream (2) from f)
in a stripper column to obtain a purified solvent-containing
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stream having a diisocyanate content of < 100 ppm and a
phosgene content of < 100 ppm, based in each case on the
weight of the purified solvent-containing stream, and
h) recycling at least a portion of the solvent-
containing stream from g) into step a).

The issue
The Examiner rejected claims 1, 2, 4, and 5 under 35 U.S.C. § 103(a)
as obvious over Sohn,2 Keggenhoff,3 and Lokum4 (Ans. 4–8).
The Examiner finds that Sohn teaches “that the phosgenation,
phosgene removal, and solvent removal steps are known: phosgene,
hydrogen chloride and solvent are taken off at the top and recirculated to the
phosgene container. The bottom product comprising isocyanate and solvent
is conveyed to a distillation, preferably a single-stage distillation, to separate
off the solvent” (Ans. 6). The Examiner finds that Keggenhoff teaches
“purification of the solvent recycle stream” (Ans. 7). The Examiner finds
that “the use of diphenylmethane is at least contemplated by Keggenhoff at,
for example, column 1” (Ans. 7).
The Examiner finds that Lokum teaches that “the use of a stripper
column to remove impurities such as phosgene from a solvent is known”
(Ans. 7)
The Examiner finds that in the “absence of some unexpected benefit,
those of ordinary skill could have made use of any known ways to purify a
solvent, such as stripping, in a predictable manner, based upon Lokum.

2 Sohn et al., US 2006/0252960 A1, published Nov. 9, 2006.
3 Keggenhoff et al., US 4,745,216, issued May 17, 1988.
4 Lokum et al., US 2003/0233013 A1, published Dec. 18, 2003.
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Accordingly, the use of a stripper column to purify a solvent stream is prima
facie obvious” (Ans. 7).
The issue with respect to this rejection is: Does the evidence of record
support the Examiner’s conclusion that Sohn, Keggenhoff, and Lokum
render the claims obvious?
Findings of Fact
1. The Specification teaches that the “production of isocyanates by
reacting a primary amine with phosgene has been adequately known from
the prior art for a relatively long time. A solution of the amine in a suitable
solvent is generally reacted with a solution of phosgene in the same solvent”
(Spec. 1, ll. 18–21).
2. Sohn teaches a process where “the reaction between organic
amine and phosgene is carried out in two or more stages in an inert solvent”
(Sohn 1 ¶ 0003).
3. Sohn teaches “a continuous process for preparing aromatic
isocyanates by mixing a stream of an aromatic amine into a phosgene stream
in a tube reactor . . . . The pressure at which the phosgene stream is
introduced into the tube reactor is 50-170 psig; the pressure of the amine
stream has to be greater in order to prevent backmixing” (Sohn 4 ¶ 0024).
4. Sohn teaches that the “liquid phase comprising isocyanate,
solvent, relatively small amounts of by-products, hydrogen chloride and
phosgene dissolved in a solvent is taken off from the second reactor
separately from the gas phase comprising hydrogen chloride, solvent,
phosgene and traces of the isocyanate” (Sohn 4 ¶ 0024).
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5. Sohn teaches that “[p]hosgene, hydrogen chloride and solvent
are taken off at the top and recirculated to the phosgene container” (Sohn 4
¶ 0025).
6. Sohn teaches that the “bottom product comprising isocyanate
and solvent is conveyed to a distillation, preferably a single-stage
distillation, to separate off the solvent. The solvent which has been separated
from the isocyanate is used for absorption of the remaining phosgene from
the hydrogen chloride stream” (Sohn 4 ¶ 0025).
7. Sohn teaches that the “uncondensed phosgene/hydrogen
chloride mixture is conveyed to a phosgene absorber into which solvent
recovered in the solvent separation is fed” (Sohn 4 ¶ 0025).
8. Keggenhoff teaches “a multi-stage process for the preparation
of polyisocyanates” (Keggenhoff, col. 2, ll. 55–56).
9. Keggenhoff teaches, in one embodiment, that after
phosgenating and separating the excess phosgene and hydrogen chloride
generated in the reaction from the reaction solvent, “the solvent together
with readily volatile compounds containing isocyanate groups” are separated
from the reaction mixture “by evaporation and recovery of the product of the
process as evaporation residue which is optionally subjected to a further
process of distillation” (Keggenhoff, col. 2, l. 58 to col. 3, l. 2).
10. Keggenhoff teaches that, after solvent recovery, the artisan may
“reuse of [sic] part of the condensate for the preparation of amine solution (i)
and of another part of the condensate for the preparation of phosgene
solution (ii)” (Keggenhoff, col. 3, ll. 5–8).
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11. Keggenhoff teaches that:
In one embodiment of this process, the total quantity
of condensates obtained in [the recovery step] may be
treated with compounds containing isocyanate reactive
hydrogen atoms, optionally after the removal of residues of
phosgene as head product by brief distillation but otherwise
without any purification by distillation, and the treated
condensate subsequently freed from the reaction products
formed by the reaction of these compounds containing
isocyanate reactive hydrogen atoms with the isocyanate-
containing compounds present in the condensate.

(Keggenhoff, col. 3, ll. 9–19.)
12. Keggenhoff teaches other prior art processes “for the
preparation of polyisocyanates in the presence of solvents, in which the
solvent is freed from traces of compounds containing isocyanate groups
before it is reused” (Keggenhoff, col. 1, ll. 41–44).
13. Keggenhoff teaches that the “solvent is treated with compounds
containing isocyanate reactive hydrogen atoms, such as alcohols or amines,
to convert the readily volatile isocyanates into reaction products containing
urethane or urea groups. The treated solvent is then separated from these
reaction products by distillation” (Keggenhoff, col. 1, ll. 44–49).
14. Keggenhoff teaches that
[U]nwanted isocyanate compounds seriously impair the
quality of the desired end products (polyisocyanates). It has
therefore been attempted to remove these impurities from
the polyisocyanate by distillation together with the solvent
after the phosgenation reaction and subsequently free the
solvent from these impurities by an elaborate column
distillation. The solvent can then be reused.

(Keggenhoff, col. 1, ll. 27–34.)
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15. Lokum teaches a
[H]eat integrated system comprising an upstream distillation
column and a downstream distillation column which are
connected in series which is used in the process for the
purification of mixtures of TDI. In this scheme the
interchanger acts as the condenser for the upstream
distillation column and as a pre-vaporizer for the
downstream distillation column. Here the solvent product P2
is removed as an overhead liquid product with no removal of
low-boilers from the solvent. In this case, the solvent
products from the upstream and downstream column are
combined and sent to a stripping column for removal of low-
boilers

(Lokum 4 ¶ 0043).
16. Lokum teaches that in a distillation process, the “remainder N
and the solvent product G from the upstream distillation column 1 are
combined to form stream P2 and fed to a stripper (not shown) to reduce the
phosgene and low-boiler concentration” (Lokum 5 ¶ 0052).
17. Lokum teaches that “[p]roduct Fraction P2 is a solvent enriched
product which is then preferably reused in the phosgenation or excess
phosgene recovery process. The fraction P2 preferably comprises solvent
with an isocyanate concentration and a phosgene concentration of less than
100 ppm by weight, respectively” (Lokum 3 ¶ 0034).
18. Lokum teaches “a schematic of the heat integrated system
comprising an upstream distillation column and a downstream distillation
column which are connected in series which is used in the process for the
purification of mixtures of TDI” (Lokum 4 ¶ 0045).
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19. Lokum teaches that “solvent products from the upstream and
downstream column are combined and sent to a stripping column for
removal of low-boilers” (Lokum 4 ¶ 0045).
20. Figure 4 of Lokum is reproduced below:

“In an alternate embodiment (FIG. 4), the solvent product G from the
interchanger 8 as well as the solvent product N from the downstream
distillation column 4 are combined to form P2 and fed to a separate stripping
column (not shown)” (Lokum 5 ¶ 0058).
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Principles of Law
Under the “law of the case” doctrine, a court will generally adhere to a
decision in a prior appeal in the same case unless one of three exceptions
exist: (1) the evidence in a subsequent trial contains new and different
material evidence; (2) there has been an intervening change of controlling
legal authority; or (3) the earlier ruling was clearly erroneous and would
work a manifest injustice. Intergraph Corp. v. Intel Corp., 253 F.3d 695,
698 (Fed. Cir. 2001); Ormco Corp. v. Align Tech., Inc., 498 F.3d 1307, 1319
(Fed. Cir. 2007); Gould, Inc. v. United States, 67 F.3d 925, 930 (Fed. Cir.
1995).
“The combination of familiar elements according to known methods
is likely to be obvious when it does no more than yield predictable results.”
KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 416 (2007). “If a person of
ordinary skill can implement a predictable variation, § 103 likely bars its
patentability.” Id. at 417.
Analysis
Our earlier decision of Appeal No. 2009-014449 is the “law of the
case” and is binding on this application. The 2009-014449 decision
therefore has a preclusive effect regarding the obviousness of combining
Sohn and Keggenhoff in a process for the production of isocyanates.
Therefore, the question before us is whether the substitution of Lokum’s
stripper column for the distillation column taught by Sohn (FF 5) and
Keggenhoff (FF 9, 11, 13) would have been obvious.
Lokum teaches that “[p]roduct Fraction P2 is a solvent enriched
product which is then preferably reused in the phosgenation or excess
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phosgene recovery process. The fraction P2 preferably comprises solvent
with an isocyanate concentration and a phosgene concentration of less than
100 ppm by weight, respectively” (Lokum 3 ¶ 0034; FF 17). Thus, Lokum
teaches that the ordinary practitioner is interested in reducing the levels of
phosgene in the solvent (FF 17). Lokum teaches the use of a stripper
column “to reduce the phosgene and low-boiler concentration” (Lokum 5
¶ 0052; FF 16).
We agree with the Examiner that the ordinary artisan, interested in
reducing phosgene levels in the isocyanate production method made obvious
by Sohn and Keggenhoff, would have reasonably incorporated Lokum’s
stripper column in order to reduce the phosgene concentrations (FF 16).
Appellants contend that Keggenhoff teaches “that a two-step
distillation process such as that required in Appellants’ invention was not
being suggested by Keggenhoff et al. Indeed, this teaching of Keggenhoff
et al would lead those skilled in the art away from Appellants’ claimed
invention” (App. Br. 4). Appellants contend that “the teaching of
Keggenhoff et al at column 1, lines 29 et seq cited by the Examiner as
support for this rejection is a description of prior art processes which did
not produce the desired polyisocyanates having the desired quality and
yields” (App. Br. 5).
We are not persuaded. Keggenhoff expressly teaches the use of two
recovery processes to separate solvent: a first evaporation and recovery
process to produce a product “which is optionally subjected to a further
process of distillation” (Keggenhoff, col. 3, ll. 1–2; FF 9). Keggenhoff’s
language reasonably suggests a multi-stage distillation, but in any case,
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Lokum expressly teaches upstream and downstream distillation columns (FF
15) as well as the combined use of a distillation column and a stripper
column (FF 16).
Also, regarding Appellants’ teaching away argument, a teaching away
requires a reference to actually criticize, discredit, or otherwise discourage
the claimed solution. See In re Fulton, 391 F.3d 1195, 1201 (Fed. Cir. 2004)
(“The prior art’s mere disclosure of more than one alternative does not
constitute a teaching away from any of these alternatives because such
disclosure does not criticize, discredit, or otherwise discourage the solution
claimed”). The teaching identified by Appellants in column 1 of
Keggenhoff does not support Appellants’ contention that the prior art “did
not produce the desired polyisocyanates having the desired quality and
yields” (App. Br. 5). Instead, Keggenhoff teaches that the solution to
unwanted isocyanate compounds is “to remove these impurities from the
polyisocyanate by distillation together with the solvent after the
phosgenation reaction and subsequently free the solvent from these
impurities by an elaborate column distillation” (Keggenhoff, col. 1, ll. 30–
34; FF 14). This teaching supports the concept of using distillation in the
process, rather than teaching away from using distillation (FF 14).
Appellants contend that “Lokum et al does not reduce the isocyanate
content of the reaction mixture in the first separation as is required in
Appellants’ claimed invention. Rather, Lokum et al first reduces the
phosgene level” (App. Br. 5). Appellants contend that “[n]ot one of the
Sohn et al, Keggenhoff et al or Lokum et al references teaches or suggests a
two-step purification process in which the diisocyanate content of the
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solvent stream is reduced in the first step and the phosgene content is
reduced in the second step as required in Appellants’ claimed invention”
(App. Br. 6).
We do not find this argument persuasive. While Appellants’ claim 1
does require first distilling the crude isocyanates solution and then purifying
the solvent stream in a stripper column, Lokum teaches a situation where a
first “crude” mixture is fed into “an upstream distillation column and a
downstream distillation column which are connected in series which is used
in the process for the purification of mixtures of TDI” (Lokum 4 ¶ 0045) (FF
18). After this distillation, the “solvent products from the upstream and
downstream column are combined and sent to a stripping column for
removal of low-boilers” (Lokum 4 ¶ 0045). Thus, Lokum teaches a situation
disclosing the order required by claim 1, where a distillation is followed by a
stripping column, to purify the solvent for reuse (FF 18–20).
Appellants contend that “it might be ‘obvious to try’ to purify MDI
using a process for purifying TDI but ‘obvious to try’ is not the standard
used to evaluate the obviousness of an invention under 35 U.S.C. §103”
(Reply Br. 2).
We note that under certain circumstances, “the fact that a combination
was obvious to try might show that it was obvious under § 103.” KSR, 550
U.S. at 421. More generally, we do not find this to be an improper “obvious
to try” situation. There would be an absolutely reasonable expectation that
the ordinary artisan would have been able to successfully incorporate
Lokum’s stripper column purification step into the distillation purification
processes of Sohn and Keggenhoff (FF 1–20). Appellants provide no
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evidence of any unpredictability in performing this combination. Kubin
stated that “[r]esponding to concerns about uncertainty in the prior art
influencing the purported success of the claimed combination, this court [in
O’Farrell] stated: ‘[o]bviousness does not require absolute predictability of
success ... all that is required is a reasonable expectation of success.”’ In re
Kubin, 561 F.3d 1351, 1360 (Fed. Cir. 2009) (citing In re O’Farrell, 853
F.2d 894, 903-904 (Fed. Cir. 1988)).
Conclusion of Law
The evidence of record supports the Examiner’s conclusion that Sohn,
Keggenhoff, and Lokum render the claims obvious.
SUMMARY
In summary, we affirm the rejection of claim 1 under 35 U.S.C.
§ 103(a) as obvious over Sohn, Keggenhoff, and Lokum. Pursuant to
37 C.F.R. § 41.37(c)(1)(vii), we also affirm the rejection of claims 2, 4, and
5, as these claims were not argued separately.

No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a).

AFFIRMED

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