Chemistry Reference
In-Depth Information
with various isotacticities. By development
of polymerization catalyst technology in
recent years,
[8-10]
it is possible to control
the tacticity of polypropylene. However,
it is difficult to directly synthesize an iPP
series with different isotacticities with only
one kind of catalyst. The study of the rela-
tionship between degradation characteris-
tics and isotacticity of iPP requires an iPP
series with systematic isotacticity variation,
and it has been difficult to synthetically
supply such iPP series in practice. A better
method is to fractionate a single iPP resin
having broad isotacticity distribution witeh
TREF to generate such a iPP series with
various isotacticities.
In this paper, two kinds of TREF appli-
cations are reported: one to evaluate the
influence of extraction of internal donor on
the change of isospecificity distribution on
MgCl
2
-supported Ziegler catalysts and the
other to clarify the relationship between the
level of tacticity and the rate of degradation
of iPP.
Cat-A: MgCl
2
(36 g; 11 m
2
/g), and EB
(7.2 ml) were placed in a 1.2 L stainless
steel vibration mill pot with 55 balls (25 mm
diameter) under nitrogen and ground for
30h at room temperature. The ground pro-
duct (200 ml) was treated with TiCl
4
(200 ml)
in a 1.0 L three-necked flask at 90
8
C for 2h
with stirring under nitrogen, followed
by washing several times with heptane
and finally stored as a toluene slurry be-
fore polymerization. The Ti content of
the catalyst was found to be 0.46 mmol-
Ti/g-cat.
Cat-B: Cat-B was prepared by the same
procedure as Cat-A, with DBP (7.2 ml)
instead of EB. The Ti content of the catalyst
was found to be 0.50 mmol-Ti/g-cat.
TiCl
3
/MgCl
2
: TiCl
3
/MgCl
2
catalyst was
prepared by grinding MgCl
2
and TiCl
3
in a
1.2 L stainless steel vibration mill pot with
55 balls (25 mm diameter) under nitrogen
atmosphere for 30 h at room temperature.
The Ti content of catalyst was 0.05 mmol-
Ti/g-cat.
Experimental Part
Extraction of Internal Donor
The MgCl
2
supported catalyst (about 1 g),
TEA (14 mmol, Al/Ti mole ratio
Materials
Research grade propylene, donated by
Tokuyama Corp., was used without further
purification. MgCl
2
was kindly supplied by
Toho Titanium Co., Ltd.
Propylene of research grade (donated
by Tokuyama Corp and Chisso Corp.),
anhydrous MgCl
2
, TiCl
4
, TiCl
3
(donated by
Toho Catalyst Co.), nitrogen (purchased
from Uno Sanso Co.), and triethylalumi-
num (TEA) (donated by Tosoh Finechem
Co.) were used without further purification.
Heptane, toluene, ethylbenzoate (EB) and
dibutylphthalate (DBP) were purified by
passage through a 13X molecular sieves
column. TEA, EB and DBP were used as
toluene solution.
30) and
toluene (200 ml) were placed in a 300 ml
flask under nitrogen and the mixture was
stirred at 30
8
C for a selected time (from 1
to 30 min). The resulting catalyst was then
recovered by filtration.
¼
Propylene Polymerization and
Estimation of Kinetic Parameters
by Stopped-Flow Method
Stopped-flow polymerization of propylene
and estimation of the kinetic parameters
were carried out according to a previ-
ously reported method.
[11-13]
The propy-
lene polymerization was typically perfor-
med with the catalyst (Cat-A or Cat-B:
ca.1.0 g) and TEA (14 mmol, Al/Ti mole
ratio
¼
Catalyst Preparation
Two types (Cat-A and Cat-B) of TiCl
4
/
MgCl
2
catalysts with two types of internal
donors and one type of TiCl
3
/MgCl
2
cata-
lyst without any donors were prepared as
follows.
C for 0.15 s.
The TEA solution in toluene (100 ml) satu-
rated with propylene (1 atm) was placed
into the vessel.
The propagation rate constant (
30) in toluene at 30
8
k
p
) and
the concentration of active sites ([C
]) were
