Ex Parte Hofer et al

Board of Patent Appeals and Interferences

Dec 13, 2008

10939498 (B.P.A.I. Dec. 13, 2008)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
____________

Ex parte FRANK HOFER, VOLKER SCHLIEPHAKE
and KLAUS MULLER-ENGEL
____________

Appeal 2008-4079
Application 10/939,498
Technology Center 1600
____________

Decided: December 13, 2008
____________

Before DONALD E. ADAMS, RICHARD M. LEBOVITZ, and
MELANIE L. McCOLLUM, Administrative Patent Judges.

LEBOVITZ, Administrative Patent Judge.

DECISION ON APPEAL
This is a decision on appeal from the final rejection of claims 1-15.
We have jurisdiction under 35 U.S.C. § 6(b). We reverse.

Appeal 2008-4079
Application 10/939,498

STATEMENT OF THE CASE
The claims are directed to a process for separating an acrylic acid with
a rectification column.
Within a rectification column, descending liquid phase (reflux
liquid) and ascending vapor phase are conducted in
countercurrent to each other. As a consequence of the
inequilibrium existing between the streams, there is heat and
mass transfer which brings about the desired separation. In
general, there are separating internals in a rectification column
to increase the mass transfer surface area.
(Spec. 4: 4-8.)
According to the Specification, “acrylic acid in the liquid phase has a
tendency” to form unwanted polymers (Spec. 2: 3-5). Consequently, when
acrylic acid is purified using a rectification column, free-radical
polymerization inhibitors are added to reduce the production of undesirable
acrylic acid polymers (id. at 2: 7-26). The Specification states that “the basis
of the present invention is the surprising finding that the presence of
diacrylic acid has a polymerization-inhibiting effect with respect to free-
radical polymerization of acrylic acid” (Spec. 3: 26-28). Claim 1, the only
independent claim on appeal, is directed to a process of purifying acrylic
acid in which diacrylic acid is ≥ 550 ppm at certain places in the rectification
column.
The Examiner rejects claims 1-15 under 35 U.S.C. § 103(a) as
obvious over the acrylic-acid separation method described in Kroker (U.S.
Pat. 5,897,749, Apr. 27, 1999) (Ans. 3-4). Claim 1, which is representative
of the rejected subject matter, reads as follows:
1. A process for rectificatively separating an acrylic acid-
containing liquid F by feeding the acrylic acid-containing liquid
F to a rectification column via a feed point Z and withdrawing a
2
Appeal 2008-4079
Application 10/939,498

stream S at a withdrawal point E above the feed point Z of the
rectification column, said stream S having a content of acrylic
acid, based on the weight of the stream S, which is ≥ 90% by
weight and is greater than the corresponding acrylic acid
content of the liquid F in % by weight, wherein the diacrylic
acid content G of the reflux liquid within the region of the
rectification column at least two theoretical plates above the
feed point Z is at least in places ≥ 550 ppm by weight based on
the weight of the reflux liquid.

ISSUE
Did the Examiner provide an adequate reason for a person of ordinary
skill in the art to have modified Kroker’s acrylic acid distillation process to
have reached the limitations of claim 1 of: 1) a “diacrylic acid content G of
the reflux liquid within the region of the rectification column at least two
theoretical plates above the feed point Z is at least in places ≥ 550 ppm by
weight based on the weight of the reflux liquid” and 2) a withdrawal point E
about a feed point Z?
PRINCIPLES OF LAW
“Although common sense directs one to look with care at a patent
application that claims as innovation the combination of two known devices
according to their established functions, it can be important to identify a
reason that would have prompted a person of ordinary skill in the relevant
field to combine the elements in the way the claimed new invention does.
This is so because inventions in most, if not all, instances rely upon building
blocks long since uncovered, and claimed discoveries almost of necessity
will be combinations of what, in some sense, is already known.” KSR Int’l
Co. v. Teleflex Inc., 127 S. Ct. 1727, 1741 (2007).
3
Appeal 2008-4079
Application 10/939,498

The “discovery of an optimum value of a result effective variable in a
known process is ordinarily within the skill of the art.” In re Boesch, 617
F.2d 272, 276 (CCPA 1980).

FINDINGS OF FACT
THE KROKER PATENT
1. Kroker describes a method of separating acrylic acid (“(meth)acrylic
acid”) in a distillation apparatus which comprises a still, condenser, and a
connection between the still and condenser (Kroker, Abstract; col. 1, ll. 12-
13).
2. The purpose of Kroker’s separation process is to separate and purify
acrylic acid from impurities (Kroker, at col. 1, l. 48 to col. 2, l. 2).
3. During Kroker’s process, “a part of the liquid content of the still”
comprising the acrylic acid “is continuously removed, superheated” in a
tubular evaporator “and recycled to the still” (Kroker, Abstract; see also at
col. 4, ll. 13-41).
4. Kroker states that the separation process can be achieved by rectification
in which “the connection between still and condenser is generally formed by
a rectification apparatus” (Kroker, at col. 3, ll. 41-43).
5. The liquid mixture comprising acrylic acid “can be continuously fed both
directly into the still itself and into the connection between still and
condenser” (Kroker, at col. 3, ll. 52-56).
6. Kroker describes a liquid starting material that comprises 2000 ppm of
diacrylic acid (Kroker, at col. 5, l. 37).
7. Figure 3 is a distillation apparatus according to Kroker, showing the still
(1), tubular evaporator utilized to superheat the liquid material comprising
4
Appeal 2008-4079
Application 10/939,498

acrylic acid (3), and a bottom product outlet (6), and a separation apparatus
(8). Kroker does not show or describe the location of the condenser.
8. The bottom product outlet 6, which is the same as the outlet 7 shown in
Figure 1, is to remove high-boiling point residue (Kroker, at col. 5, ll. 16-18;
col. 2, ll. 64-67).
Claim 1
9. Claim 1 is directed to a two-step process comprising: 1) feeding a liquid
F into a rectification column through feed point Z; and 2) withdrawing
stream S comprising acrylic acid from the rectification column at withdrawal
point E, which is above feed point Z.
10. According to claim 1, the diacrylic acid content G of “the reflux liquid
within the region of the rectification column at least two theoretical plates
above the feed point Z is at least in places ≥ 550 ppm by weight based on the
weight of the reflux liquid.”
The Specification
11. A “normally undesired accompanying phenomenon of acrylic acid in
[the] condensed phase [found in a rectification column] is the formation of
[acrylic acid] oligomers” such as diacrylic acid (Spec. 2: 38-41).
12. “As a consequence of the significantly different boiling points, it is
possible to remove diacrylic acid from acrylic acid in a simple manner by
rectification. Diacrylic acid accumulates in the lower section of the
rectification column and acrylic acid in the upper section of the rectification
column which is normally substantially predominantly free of diacrylic acid”
(Spec. 3: 14-18).
13. The Specification states that “the basis of the present invention is the
surprising finding that the presence of diacrylic acid has a polymerization-
5
Appeal 2008-4079
Application 10/939,498

inhibiting effect with respect to free-radical polymerization of acrylic acid”
(Spec. 3: 26 to 4:2).
14. According to the Specification, the purpose of keeping the diacrylic acid
content at 550 ppm or greater is to inhibit unwanted polymerization between
acrylic monomers in the rectification column (Spec 2: 3-27; 3: 26 to 4: 2).
15. The Specification states that the phrase “theoretical plates” as used in
claim 1 encompasses “[m]ass transfer trays on which there is equilibrium
between descending [reflux] liquid and ascending vapor,” as well as “other
separating internals which are suitable for countercurrent rectification”
(Spec. 4: 4-20).
16. Acrylic acid is stated to be a part of the low boiler stream (Spec. 17: 15-
32), not the high boiler fraction which condenses at the bottom of the
rectification column (Spec. 15: 25-42).
Differences between the Kroker and claim 1
17. Kroker does not expressly describe withdrawing stream S comprising
acrylic acid from the rectification column at withdrawal point E, which is
above feed point Z, as required by claim 1 (see Ans. 5).
18. Kroker also does not describe claim 1’s limitation of a diacrylic acid
content of ≥ 550 ppm at least in places of the rectification column “at least
two theoretical plates above the feed point Z” (see Ans. 5).
Reason to modify Kroker
19. The Examiner states that from Kroker’s teachings “it is within the
purview of the skilled artisan in the art to . . . [make] a suitable choice for
the diacrylic acid content G of the reflux at least two theoretical plates above
the feed point by routine experimentation” (Ans. 5-6). The Examiner also
6
Appeal 2008-4079
Application 10/939,498

states that it would have been routine to choose a “withdrawal point E”
above a “feed point Z” (id).
ANALYSIS
The differences between Kroker and the claimed invention are that
Kroker does not disclose: 1) a reflux fluid in a rectification column having a
content of ≥ 550 ppm of diacrylic acid at least in places at least two theoretic
plates above a feed point Z through which a liquid comprising acrylic acid is
introduced; and 2) a withdrawal point E above a feed point Z (FF17-18).
The Examiner acknowledges that these limitations are not met by Kroker,
but asserts that it would have been obvious to persons of skill in the art to
choose them in order to optimize Kroker’s rectification process (Ans. 5-6;
FF19).
We do not agree with the Examiner’s analysis. Kroker’s disclosure
about using a rectification column to separate acrylic acid from a starting
material is at best sketchy. Kroker states that a rectification column can be
used in its separation process, and says that it is between the still and
condenser (FF4). However, Kroker does not describe the condenser’s
location (see FF4, 7). Consequently, it is unclear exactly where the
rectification column would be placed.
In addition, Kroker specifically states at what location the liquid
mixture comprising impure acrylic acid is fed into the rectification column
but not where the liquid is removed. Kroker discloses that the liquid mixture
can fed into the still or connection between the still and condenser (FF5), but
there is no evidence in the record that removing the stream at a point about
where the liquid is introduced (“feed point Z”) as required by claim 1 would
have been the routine choice by persons of skill in the art (FF19)
7
Appeal 2008-4079
Application 10/939,498

In particular, the Examiner pointed to bottom outlet 6 of Figure 2 as
corresponding to the withdrawal point E of claim 1, and contends it is above
the feed point Z as in claim 1 (Ans. 6). We agree with Appellants that
bottom outlet 6 is not described by Kroker as a withdrawal point for acrylic
acid. Rather, Kroker states that the bottom outlet is for removing high-
boiling point residues (FF8). Persons of ordinary skill in the art would have
recognized that acrylic acid is part of the low boiler stream, not the high
boiler fraction that condenses at the bottom of the rectification column and
which would be removed by the bottom outlet (FF16).
Likewise, there is no evidence or logical reasoning that would have
directed persons of skill in the art to a diacrylic content of ≥ 550 ppm at least
in places of the rectification column “at least two theoretical plates above the
feed point Z” as recited in claim 1. To establish obviousness, it is generally
necessary to provide a reason to have modified the prior art to arrive at the
claimed invention. KSR Int’l Co. v. Teleflex Inc., 127 S. Ct. at 1741. The
Examiner has not established an evidentiary basis for optimizing the
diacrylic acid content to the value and theoretical plate position in the
column as required by claim 1. Even were diacrylic acid to have been
recognized as a result-effective variable whose optimal value would have
been routinely discovered by persons of ordinary skill in the art (see In re
Boesch, 617 F.2d 272, 276 (CCPA 1980)), the Examiner has not provided a
reason to have required it to be above or equal to 550 ppm. As pointed out
by Appellants, the purpose of rectification is to separate acrylic acid from
contaminants, including diacrylic acid (FF2, 11, 12; App. Br. 4). Thus, it is
not evident why the skilled worker would have sought to optimize the
8
Appeal 2008-4079
Application 10/939,498

concentration of diacrylic acid in the rectification column above a certain
threshold.
The Examiner takes the position that it would be reasonable to assume
that starting with a liquid mixture having a content of 2000 ppm of diacrylic
acid as described in Kroker (FF6) would result in a diacrylic acid at least ≥
550 ppm two theoretic plates above feed point Z (Ans. 7). However, the
Examiner has not provided a reasonable basis for believing that a process,
whose goal was to separate acrylic acid from other contaminating
components (FF2), would result in the claimed amount of diacrylic acid at
the position in the column required by claim 1. To the contrary, the
Specification teaches that diacrylic acid accumulates in the lower part of the
column and is absent from the upper part of the column (FF12; App. Br. 5).
Thus, the evidence of record appears to be inconsistent with the Examiner’s
assumption.

CONCLUSION OF LAW
Because the Examiner did not provide adequate reason for persons of
ordinary skill in art to have modified Kroker’s acrylic acid distillation
process to have reached the subject matter of claim 1, we reverse its
rejection under 35 U.S.C. § 103(a) and dependent claims 2-15.

REVERSED

dm

9
Appeal 2008-4079
Application 10/939,498

OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT,
1940 DUKE STREET
ALEXANDRIA, VA 22314

10