Appeal No. 1998-3272
Application 08/461,393
R3 position of the metallocene compounds of Winter ‘178 can be used as the bridging groups in
the R″ position of the metallocene compounds of Ewen with the reasonable expectation of
obtaining stereorigid metallocene compounds that are used as the transition metal component of
a catalyst used to prepare syndiotactic polyolefins.6
The examiner points out that “Ewen discloses that metallocenes having different
cyclopentadienyl rings such as cyclopentadienyl and fluorenyl connected by a structural bridge
which imparts stereorigidity to the rings, produces a catalyst (when combined with aluminoxane)
that will produce syndiotactic polymers of alpha-olefins having 3 or more carbon atoms”
(answer, page 4). The examiner further points out that Winter ‘178 also teaches “bridges that
will produce stereorigid chiral metallocenes” with respect to formula member R3, which “are
generically disclosed by Ewen, e.g., hydrocarbyl radicals containing silicon, germanium,
phosphorous, nitrogen, boron or aluminum” (id., pages 4-5). The examiner also finds that the
teachings of Winter ‘178 at col. 2, line 55, would include ring structures as required by appealed
claim 36 (id., page 5).
We agree with the examiner’s evidentiary findings as Ewen discloses that the two
cyclopentadienyl or “Cp” rings are different and can be the mononuclear cyclopentadienyl and
the polynuclear fluorenyl; that zirconium dichloride can be the substituted central transition
metal atom (e.g., col. 3, lines 24-25; col. 4, line 64, to col. 5, line 12; and col. 5, lines 37-40); and
that bridging group “R″ is a structural bridge between two [cyclopentadienyl] rings imparting a
stereorigidity to the [cyclopentadienyl] rings” (col. 3, lines 26-28; see also col. 4, lines 54-56)
which “is preferably selected from the group consisting of an alkyl radical selected from the
group of an alkyl radical having 1-4 carbon atoms or a hydrocarbyl group containing silicon,
germanium, phosphorous, nitrogen, boron or aluminum” (col. 4, lines 56-60). Ewen also
discloses that the central transition metal atom can be, inter alia, titanium and zirconium (e.g.,
col. 5, lines 26-29).
Winter ‘178 also discloses that the two cyclopentadienyl rings can be different and can be
mono- and polynuclear, with zirconium dichloride as the substituted central transition metal atom
6 We have considered only Ewen and Winter ‘178 with respect to this dispositive issue as the
examiner does not rely on Welborn and Kioka in this respect (answer, page 5) and appellants
- 5 -
Page: Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Next
Last modified: November 3, 2007