Chemistry Reference
In-Depth Information
140
C, and a part of the solution (ca. 6 ml)
was passed through the fractionation col-
umn, which was slowly cooled down at
6.7
8
C/h from 140
8
Cto20
8
C. Elution of the
deposited iPP with ODCB at a flow rate of
150 ml/h was first carried out at 20
8
C for
30 min to obtain the ODCB-soluble frac-
tion, and then the column was heated at
16
8
C/h up to 140
8
C. The eluted iPP solu-
tion was analyzed by a refractive index
detector to obtain the TREF diagram.
Moreover, tacticity fractions of the iPP
with increasing crystallinity were then eluted
with ODCB at the temperatures increasing
stepwise from 20
8
C to 140
8
C divided into
5 steps (20, 60, 90, 106 and 140
8
C). Polymer
was eluted during 90 min at every step after
the temperature had stabilized for 30 min.
The fraction was then collected and pre-
cipitated in methanol. All fractionated iPP
were TREF fractions insoluble below 20
8
Figure 2.
Content of residual internal donor as a function of the
extraction time.
part of the solution (50 ml, ca. 20 mg/ml) was
eluted through the fractionation column.
The column was then cooled to 20
8
Cslowly
(6.7
C/h). Elution with ODCB (150 ml/h)
was first carried out at 20
8
C for 30 min
to obtain the ODCB-soluble fraction, and
then the column was heated up to 140
8
Cat
10
8
C.
The weight fraction of the soluble part
(below 20
8
C) was 52 wt%, and its mole-
cular weight and tacticity were very low
(M
n
¼
8
C/h.
The precise fractionation of iPP was
carried out with the same TREF device,
solvent, and column. About 70 mg of the
iPP was dissolved in 10 ml of ODCB at
25 mol%). Since
this soluble part was considered to contain
impurities, such as unsaturated polymer
chain end groups, for promoting degrada-
tion,
[10]
6,000 and mmmm
¼
8
it was completely removed.
Figure 3.
TREF diagrams of iPPs obtained from the extracted Cat-A.
