Chemistry Reference
In-Depth Information
30
With CSA ATREF (0.877 g/cc, 1MI)
No CSA ATREF (0.89 g/cc, 1MI)
Mol % Octene of OBC Fractions
Mol % Octene of Blend Fractions
Random Copolymer Fractions from
Z-N LLDPE and mLLDPE
25
"Non Crystallizable
Fraction"
20
15
OBC Fractions
10
5
0
20
40
60
80
100
TREF Elution Temperature (
°
C)
Figure 5.
Comonomer versus elution temperature of OBC.
Figure 5 and Tables 5-6 show the results
for the OBC and in-reactor blend. Strik-
ingly, it can be seen that for a given ATREF
elution temperature, the octene content of
the preparative fractions from the OBC
copolymer is significantly higher than that
of the preparative fractions from traditional
random copolymers.
The expected comonomer composition
versus elution temperature is shown by the
calibration line for random copolymers. In
terms of the distribution of comonomer in
this OBC,
comonomer distribution is statistically non-
random and highly blocked (or segmented).
Thus, for the high elution temperatures
observed, the comonomer content of the
fractions is significantly higher due to the
presence of the octene-rich soft segment
within the chain. In comparison, the octene
content of the fraction from the in-reactor
blend produced with no chain shuttling
agent falls along the random copolymer line
as expected.
it can be concluded that the
Random Versus Block Copolymers
The observation that the TREF fractions
from an OBC contain a higher than
expected amount of comonomer demon-
strates that the intrachain comonomer
distribution or
Table 5.
OBC TREF fractionation results.
OBC TREF Fractionation (0.8786 g/cc, 1.5 I2)
Fractionation
Temperature
(
8
C)
sequence distribution is
Weight
Fraction
Recovered
ATREF T
(
8
C)
Mol %
Octene
(NMR)
Table 6.
In-reactor blend TREF fractionation results.
20
0.162
20
14.1
20-60
0.104
67
13.7
BLEND TREF Fractionation (0.8895 g/cc, 0.9 I2)
Fractionation
Temperature
(
8
C)
60-65
0.040
70.5
12.6
65-70
0.053
73
12.2
Weight
Fraction
recovered
ATREF T
(
8
C)
Mol %
Octene
(NMR)
70-75
0.126
77
11.7
75-80
0.220
81
10.5
80-85
0.192
84
9.8
85-90
0.065
88.5
7.0
20
0.63
20
14.5
90-95
0.019
92
5.2
20-105
0.37
96
0.6
