Ex parte BREKAU et al.

Board of Patent Appeals and Interferences

Dec 15, 1998

08067308 (B.P.A.I. Dec. 15, 1998)

Application for patent filed May 26, 1993.1
1
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
The opinion in support of the decision being entered today (1)
was not written for publication in a law journal and (2) is
not binding precedent of the Board.
Paper No. 20
UNITED STATES PATENT AND TRADEMARK OFFICE
_____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_____________
Ex parte UWE BREKAU, HANS-DIETER BLOCK, HANS-HEINRICH
MORETTO,
PETER SCHMIDT, PETER SCHOBER and WERNER LUDOVICI
_____________
Appeal No. 95-2237
Application 08/067,3081
______________
HEARD: November 6, 1998
_______________
Before KIMLIN, JOHN D. SMITH and WEIFFENBACH, Administrative
Patent Judges.
KIMLIN, Administrative Patent Judge.
DECISION ON APPEAL
This is an appeal from the final rejection of claim 1,
the only claim in the present application. Claim 1 reads as
follows:
Appeal No. 95-2237
Application 08/067,308
2
1. A continuous process for the preparation of aqueous
alkaline silica sols which contain non-aggregated,
spherical Si0 particles with an average diameter of 27-722
nm, from an acidic fresh sol which contains 4-8% by
weight of Si0 in the form of particles having an average2
particle diameter of about 2 nm at a pH value of 2-4 and
which has been prepared by mixing an alkali silicate
solution with a cation exchanger resin in the H-form,
this acidic fresh sol is added to a starting medium
containing an aqueous, alkaline, colloidal silica sol
solution having a pH value of >8, a Si0 content of 2-20%2
by weight and an average particle size of 14-27 nm,
alkaline agents are added to this medium at temperatures
near the boiling point thereof in such quantities that
the pH value does not fall below 8 during the whole
process, and the addition of acidic fresh sol and
alkaline agents is continued until the particles have an
average diameter of 27-72 nm and the aqueous, alkaline
silica sols thus prepared are concentrated, characterised
(sic)in that
a) the acidic fresh sol is continuously
introduced into the reactors of a multi-stage
reaction cascade, in which the first stage
contains the starting medium and each successive
reactor of the cascade is supplied with overflow
from the preceding reactor, and the pH value in
the reactors must not fall below 8,
b) alkaline agents, preferably alkaline sodium
silicate solution, alkaline potassium silicate
solution, sodium hydroxide solution, potassium
hydroxide solution, are continuously introduced
into the first reactor or into the first
reactors in such a quantity that a pH value of 8
Appeal No. 95-2237
Application 08/067,308
3
to 12.5 is established in the reactors thus
charged,
c) the average residence times in the stages of
the reaction cascade charged with acidic fresh
sol are adjusted in such a manner that an
average particle size of 27-72 nm is obtained in
the last reactor of the cascade.
The examiner relies upon the following references as
evidence of obviousness:
Weldes et al. (Weldes) 3,440,175 Apr. 22, 1969
Leutner et al. (Leutner) 4,336,234 Jun. 22, 1982
Appellants' claimed invention is directed to a continuous
process for the production of aqueous alkaline silica sols
with SiO particles having an average diameter of 27-72 nm. 2
The process entails preparing an acidic fresh sol having SiO2
particles with an average diameter of about 2nm by mixing an
alkali silicate solution with a cation exchanger resin in the
H-form, and then adding the acidic fresh sol to a starting
medium containing an aqueous, alkaline, colloidal silica sol
solution having an SiO content of 2-20% by weight and an2
average particle size of 14-27 nm. The continuous process is
carried out in a multi-stage casade reactor by continuously
introducing the acidic fresh sol into the reactor wherein the
Appeal No. 95-2237
Application 08/067,308
4
first stage contains the starting medium.
Appealed claim 1 stands rejected under 35 USC § 103 as
being unpatentable over Weldes in view of Leutner.
Upon careful consideration of the opposing arguments pre-
sented on appeal, we agree with appellants that the prior art
applied by the examiner fails to establish a prima facia case
of obviousness for the claimed subject matter. Accordingly,
we will not sustain the examiner's rejection.
Appellants submit on page 3 of the brief that although
Weldes refers to the disclosed process as a "continuous" one,
the reference does not actually describe a true continuous
process, i.e. one that achieves steady-state conditions.
According to appellants, the examples and claim 4 of Weldes
illustrate that the reference employs a batch process rather
than a continuous process. The examiner, on the other hand,
rather than offer a critical refutation of appellants'
analysis of the Weldes process, simply adheres to Weldes' use
of the term "continuous". Accordingly, at issue left for our
resolution is whether the combined teachings of Weldes and
Leutner establish the obviousness of a continuous process of
Appeal No. 95-2237
Application 08/067,308
5
the type claimed.
The examiner recognizes that Weldes does not teach the
use of the claimed multi-stage reactor. According to the
examiner, Leutner's use of a multi-stage cascade reactor to
produce alum-inosililcate suspensions would have made it
obvious for one of ordinary skill in the art to use such a
cascade reactor in the process of Weldes.
We cannot sustain the examiner's position because, in the
face of appellants' argument, the examiner has not established
either a close correspondence between the specific process
steps of appellants and Weldes, or that one of ordinary skill
in the art would have considered the multi-stage cascade
process of Leutner, which is directed to the preparation of
silicate suspensions, a suitable process for preparing aqueous
alkaline silica sols. In our view, the examiner's rejection
is tantamount to saying that it would have been obvious for
one of ordinary skill in the art to use any known,
conventional continuous reactor in the process of Weldes.
However, there is a distinct lack of evidentary support for
such legal conclusion.
Appeal No. 95-2237
Application 08/067,308
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Also, the claimed porcess requires that the starting
medium is a colloidal silica sol containing at least 2% by
weight of SiO . However, the starting material of Weldes is2
an alkaline solution that "may contain no silica at all or
merely that which results from using an alkali silicate
solution diluted to the desired pH." (col. 2, lines 21-23).
Hence, although the starting material of Weldes may apparently
contain some incidental silica, the examiner has not
established that it would have been obvious
from the teaching of Weldes to employ a starting material that
is a silica sol having the claimed SiO content of 2-20% by2
weight. In particular, the examiner has not made out the case
that by following the teachings of Weldes for forming a
starting material, the claimed starting material containing a
silica sol solution having the recited amount of SiO would2
necessarily, or inherently, result.
In conclusion, based on the foregoing, the examiner's
decision rejecting the appealed claim is reversed.
REVERSED
Appeal No. 95-2237
Application 08/067,308
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EDWARD C. KIMLIN )
Administrative Patent Judge )
)
)
) BOARD OF PATENT
JOHN D. SMITH ) APPEALS AND
Administrative Patent Judge ) INTERFERENCES
)
)
)
CAMERON WEIFFENBACH )
Administrative Patent Judge )
vsh
Appeal No. 95-2237
Application 08/067,308
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